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position:absolute

By Stephen Bucaro

Default Positioning

One of the most important CSS webpage layout concepts to understand is how to position webpage elements. Every element on a webpage, be it an image, a drop-down list, or just a paragraph of text, is actually a rectangular box, referred to as an element. When a Web browser loads an html file, it parses the html code from left-to-right top-to-bottom, just as we would read it and, by default, it renders the webpage, by placing elements on the webpage from left-to-right and from top-to-bottom. You can think of this as the webpage elements as "flowing" into position. As the elements flow onto the webpage, they line themselves up along a "baseline".

Webpage elements that flow into position from left-to-right are called inline elements. If there isn't enough room to the right to place an element, the browser places it on the next line. Certain elements, like paragraphs <p>, divisions <div>, and horizontal rules <hr />, called block elements, do not normally flow on the webpage from left-to-right. Block elements, by default, start on a new line, causes the next element in the flow to start a new line.

The style rule position is used to override this default behavior. The value of the position element may be set to relative, absolute, or fixed. In this article, I'll describe the effect of setting the style rule position: relative.

Shown below is the code for a webpage containing three span elements and how they would be rendered by default in the browser.

<html>
<head>

<style type="text/css">
.myBox
{
background-color:crimson;
border-style:solid;
border-width:1px;
padding:4px;
}
</style>

</head>
<body>

<span class="myBox">Element 1</span>
<span class="myBox">Element 2</span>
<span class="myBox">Element 3</span>

</body>
</html>

Absolute Positioning

When you specify an element's position:absolute you can relocate the element to the exact position where you want it to go. You can use the left and ⁄ or top property to place the element exactly where you want on the webpage.

<html>
<head>

<style type="text/css">
.myBox
{
background-color:crimson;
border-style:solid;
border-width:1px;
padding:4px;
width:80px;
}
#myAbs
{
position:absolute;
left:40px;
top:30px;
background-color:crimson;
border-style:solid;
border-width:1px;
padding:4px;
width:80px;
}
</style>

</head>
<body>

<span class="myBox">Element 1</span>
<span id="myAbs">Element 2</span>
<span class="myBox">Element 3</span>

</body>
</html>

Absolute Positioning

Note that Element 2 is absolute positioned 40 pixels to the right and 30 pixels down from the upper-left corner of its containing element (the <body> element).

Note that the values of left and top are offsets relative to the element's containing element NOT offsets with respect to another element. Other elements, even other absolute positioned elements are not affected by the offsets, so the absolute positioned element could overlap other elements.

More CSS Quick Reference:
• Context selectors
• Specifying Color
• Set the Word Spacing
• Indent the First Line of Text
• nth-child Selector
• Set the Font Properties
• Use an External Style Sheet
• CSS background-clip Property
• Style the First Line
• Set a Background Image