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Learn how to position HTML elements on various parts of a web page.

Display and Positioning

Great job! In this lesson, you learned how to control the positioning of elements on a web page.

Let's review what you've learned so far:

* The `position` property allows you to specify the position of an element.
* When set to `relative`, an element's position is relative to its default position on the page.
* When set to `absolute`, an element's position is relative to its closest positioned parent element. It can be pinned to any part of the web page, but the element will still move with the rest of the document when the page is scrolled.
* When set to `fixed`, an element's position can be pinned to any part of the web page. The element will remain in view no matter what.
* When set to `sticky`, an element can stick to a defined offset position when the user scrolls its parent container.
* The `z-index` of an element specifies how far back or how far forward an element appears on the page when it overlaps other elements.
* The `display` property allows you to control how an element flows vertically and horizontally in a document.
* `inline` elements take up as little space as possible, and they cannot have manually adjusted `width` or `height`.
* `block` elements take up the width of their container and can have manually adjusted `height`s.
* `inline-block` elements can have set `width` and `height`, but they can also appear next to each other and do not take up their entire container width.
* The `float` property can move elements as far left or as far right as possible on a web page.
* You can clear an element's left or right side (or both) using the `clear` property.

When combined with an understanding of the box model, positioning can create visually appealing web pages. So far, we've focused on adding content in the form of text to a web page. In the next unit, you'll learn how to add and manipulate images to a web page.

Review: Layout

When an element's position is set to `absolute`, as in the last exercise, the element will scroll with the rest of the document when a user scrolls.

We can _fix_ an element to a specific position on the page (regardless of user scrolling) by setting its position to `fixed`, and accompanying it with the familiar offset properties `top`, `bottom`, `left`, and `right`.

```css
.title {
  position: fixed;
  top: 0px;
  left: 0px;
}
```

In the example above, the `.title` element will remain fixed to its position no matter where the user scrolls on the page, like in the image below:

![Diagram of position fixed](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/Fixed.gif)

This technique is often used for navigation bars on a web page.


Position: Fixed

The third value for the `display` property is `inline-block`. Inline-block display combines features of both inline and block elements. Inline-block elements can appear next to each other and we can specify their dimensions using the `width` and `height` properties. Images are the best example of default inline-block elements.

For example, the `<div>`s below will be displayed on the same line and with the specified dimensions:

![inline block example](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/display-inline-block.png) 

Let's take a look at the code:

```html
<div class="rectangle">
  <p>I’m a rectangle!</p>
</div>
<div class="rectangle">
  <p>So am I!</p>
</div>
<div class="rectangle">
  <p>Me three!</p>
</div>
```

```css
.rectangle {
  display: inline-block;
  width: 200px;
  height: 300px;
}
```

There are three rectangular divs that each contain a paragraph of text. The `.rectangle` `<div>`s will all appear inline (provided there is enough space from left to right) with a width of 200 pixels and height of 300 pixels, even though the text inside of them may not require 200 pixels by 300 pixels of space.


Display: Inline-Block

Since `static` and `relative` positioned elements stay in the normal flow of the document, when a user scrolls the page (or parent element) these elements will scroll too. And since `fixed` and `absolute` positioned elements are removed from the document flow, when a user scrolls, these elements will stay at their specified offset position. 

The `sticky` value is another position value that keeps an element in the document flow as the user scrolls, but *sticks* to a specified position as the page is scrolled further. This is done by using the `sticky` value along with the familiar offset properties, as well as one new one. 

```css
.box-bottom {
  background-color: darkgreen;
  position: sticky;
  top: 240px;
}
```

In the example above, the `.box-bottom` `<div>` will remain in its relative position, and scroll as usual. When it reaches 240 pixels from the top, it will stick to that position until it reaches the bottom of its parent container where it will "unstick" and rejoin the flow of the document.

![Diagram of an element with sticky position](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/Sticky.gif)

Position: Sticky

Another way of modifying the position of an element is by setting its position to `absolute`.

When an element's position is set to `absolute`, all other elements on the page will ignore the element and act like it is not present on the page. The element will be positioned relative to its closest positioned parent element, while offset properties can be used to determine the final position from there. Take a look at the image below:

![Diagram of an element with absolute position, as described in the following paragraph](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/position-absolute.png)

The "This website is in progress. Please come back later!" text is displaced from its static position at the top left corner of its parent container. It has offset property declarations of `top: 300px;` and `right: 0px;`, positioning it 300 pixels down, and 0 pixels from the right side of the page.

Position: Absolute

One way to modify the default position of an element is by setting its `position` property to `relative`.

This value allows you to position an element _relative_ to its default static position on the web page. 

```css
.green-box {
  background-color: green;
  position: relative;
}
```

Although the code in the example above instructs the browser to expect a relative positioning of the `.green-box` element, it does not specify where the `.green-box` element should be positioned on the page. This is done by accompanying the `position` declaration with one or more of the following *offset properties* that will move the element away from its default static position:

* `top` - moves the element down from the top.
* `bottom` - moves the element up from the bottom.
* `left` - moves the element away from the left side (to the right).
* `right` - moves the element away from the right side (to the left).

You can specify values in pixels, ems, or percentages, among others, to dial in exactly how far you need the element to move. It's also important to note that offset properties will not work if the element's `position` property is the default `static`.

```css
.green-box {
  background-color: green;
  position: relative;
  top: 50px;
  left: 120px;
}
```

In the example above, the element of `green-box` class will be moved down 50 pixels, and to the right 120 pixels, from its default static position. The image below displays the new position of the box.

![Diagram of an element with relative position](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/Relative.png)

Offsetting the relative element will not affect the positioning of other elements. 

Position: Relative

A browser will render the elements of an HTML document that has no CSS from left to right, top to bottom, in the same order as they exist in the document. This is called the _flow_ of elements in HTML.  

In addition to the properties that it provides to style HTML elements, CSS includes properties that change how a browser _positions_ elements.  These properties specify where an element is located on a page, if the element can share lines with other elements, and other related attributes. 

In this lesson, you will learn five properties for adjusting the position of HTML elements in the browser: 

* `position`
* `display`
* `z-index` 
* `float`
* `clear`

Each of these properties will allow us to position and view elements on a web page. They can be used in conjunction with any other styling properties you may know.



Flow of HTML

Every HTML element has a default `display` value that dictates if it can share horizontal space with other elements. Some elements fill the entire browser from left to right regardless of the size of their content. Other elements only take up as much horizontal space as their content requires and can be directly next to other elements.

In this lesson, we’ll cover three values for the `display` property: `inline`, `block`, and `inline-block`.

The default `display` for some elements, such as `<em>`, `<strong>`, and `<a>`, is called _inline_. Inline elements have a box that wraps tightly around their content, only taking up the amount of space necessary to display their content and not requiring a new line after each element. The height and width of these elements cannot be specified in the CSS document. For example, the text of an anchor tag (`<a>`) will, by default, be displayed on the same line as the surrounding text, and it will only be as wide as necessary to contain its content. `inline` elements cannot be altered in size with the `height` or `width` CSS properties.

```html
To learn more about <em>inline</em> elements, read <a href="#">MDN documentation</a>.   
```

In the example above, the `<em>` element is `inline`, because it displays its content on the same line as the content surrounding it, including the anchor tag. This example will display:

To learn more about _inline_ elements, read <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Inline_elements" target="_blank" rel="noopener noreferrer">MDN documentation</a>.

The CSS `display` property provides the ability to make any element an inline element. This includes elements that are not inline by default such as paragraphs, divs, and headings.

```css
h1 {
  display: inline;
}
```

The CSS in the example above will change the display of all `<h1>` elements to `inline`. The browser will render `<h1>` elements on the same line as other inline elements immediately before or after them (if there are any).

Inline Display

Some elements are not displayed in the same line as the content around them. These are called _block-level_ elements. These elements fill the entire width of the page by default, but their `width` property can also be set. Unless otherwise specified, they are the height necessary to accommodate their content. 

Elements that are block-level by default include all levels of heading elements (`<h1>` through `<h6>`), `<p>`, `<div>` and `<footer>`.  For a complete list of block level elements, visit <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Block-level_elements" target="_blank">the MDN documentation</a>.  

```css
strong {
  display: block;
}
```
In the example above, all `<strong>` elements will be displayed on their own line, with no content directly on either side of them even though their contents may not fill the width of most computer screens.


Display: Block

When boxes on a web page have a combination of different positions, the boxes (and therefore, their content) can overlap with each other, making the content difficult to read or consume.

```css
.blue-box {
  background-color: blue;
}

.green-box {
  background-color: green;
  position: relative;
  top: -170px;
  left: 170px;
}
```

In the example above, the `.green-box` element overlaps on top of the `.blue-box` element.

The `z-index` property controls how far back or how far forward an element should appear on the web page when elements overlap. This can be thought of as the _depth_ of elements, with deeper elements appearing behind shallower elements.

The `z-index` property accepts integer values. Depending on their values, the integers instruct the browser on the order in which elements should be layered on the web page.

```css
.blue-box {
  background-color: blue;
  position: relative;
  z-index: 1;
}

.green-box {
  background-color: green;
  position: relative;
  top: -170px;
  left: 170px;
}
```

In the example above, we set the `.blue-box` position to `relative` and the z-index to 1. We changed position to `relative`, because the `z-index` property does _not_ work on static elements. The z-index of `1` moves the `.blue-box` element forward, because the `z-index` value has not been explicitly specified for the `.green-box` element, which means it has a default `z-index` value of 0. Take a look at the example image below:

![Diagram of z-index](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/Z-index.png)

Z-Index

Take a look at the _block-level_ elements in the image below:

![Diagram of block-level elements](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/Position-updated.png)

Block-level elements like these boxes create a _block_ the full width of their parent elements, and they prevent other elements from appearing in the same horizontal space.

Notice the block-level elements in the image above take up their own line of space and therefore don't overlap each other. In the browser to the right, you can see block-level elements also consistently appear on the left side of the browser. This is the default _position_ for block-level elements.

The default position of an element can be changed by setting its `position` property. The `position` property can take one of five values:
* `static` - the default value (it does not need to be specified)
* `relative`
* `absolute`
* `fixed`
* `sticky`

In the next few exercises, you'll learn about the values in the list above. For now, it's important to understand that if you favor the default position of an HTML element, you don't need to set its `position` property.

Position

So far, you've learned how to specify the exact position of an element using offset properties. If you're simply interested in moving an element as far left or as far right as possible in the container, you can use the `float` property. 

The `float` property is commonly used for wrapping text around an image. Note, however, that moving elements left or right for layout purposes is better suited for tools like CSS grid and flexbox, which you'll learn about later on.

The `float` property is often set using one of the values below:

* `left` - moves, or floats, elements as far left as possible.
* `right` - moves elements as far right as possible.

```css
.green-section {
  width: 50%;
  height: 150px;
}

.orange-section {
  background-color: orange;
  width: 50%;
  float: right;
}
```

In the example above, we float the `.orange-section` element to the `right`. This works for static and relative positioned elements. See the result of the code below:

![Diagrm of an element floating on the right](https://static-assets.codecademy.com/Courses/Learn-CSS/Display-Position/Float.png)

Floated elements must have a width specified, as in the example above. Otherwise, the element will assume the full width of its containing element, and changing the float value will not yield any visible results.

Float

The `float` property can also be used to float multiple elements at once. However, when multiple floated elements have different heights, it can affect their layout on the page. Specifically, elements can "bump" into each other and not allow other elements to properly move to the left or right.

The `clear` property specifies how elements should behave when they bump into each other on the page. It can take on one of the following values:

* `left`&mdash;the left side of the element will not touch any other element within the same containing element.
* `right`&mdash;the right side of the element will not touch any other element within the same containing element.
* `both`&mdash;neither side of the element will touch any other element within the same containing element.
* `none`&mdash;the element can touch either side.

```css
div {
  width: 200px;
  float: left;
}

div.special {
  clear: left;
}
```

In the example above, all `<div>`s on the page are floated to the left side. The element with class `special` did not move all the way to the left because a taller `<div>` blocked its positioning. By setting its `clear` property to `left`, the `special` `<div>` will be moved all the way to the left side of the page.