Cascading style sheets are great for building all sorts of eye-catching background effects for web pages. CSS allows the utilization of JPG, PNG and GIF images, which can be easily repeated along the X and Y coordinates. This facilitates the creation of professional-looking web documents by using only a few tiny background graphics that can be downloaded quickly by way of a browser.
Using PNG Images to Build Background Effects - Building a basic background gradient using a GIF image (Page 3 of 4 )
As I stated in the section that you just read, constructing a smooth background gradient using a small GIF image requires practically the same techniques that I used previously when utilizing a JPG graphic. In this case, I’m going to use the sample web page that you saw earlier to demonstrate how this gradient can be built with minor hassles.
Having explained my approach, please have a close look at the below (X)HTML file, which performs this task in a few simple steps:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Sample web page with GIF-based background</title>
<h1>This is the header section of the web page</h1>
<p>Contents for header section go here. Contents for header section go here. Contents for header section go here. Contents for header section go here.</p>
</div>
<div id="navbar">
<h1>This is the navigation bar of the web page</h1>
<ul>
<li><a href="#">Link 1</a></li>
<li><a href="#">Link 2</a></li>
<li><a href="#">Link 3</a></li>
<li><a href="#">Link 4</a></li>
<li><a href="#">Link 5</a></li>
<li><a href="#">Link 6</a></li>
</ul>
</div>
<div id="mainwrapper">
<div id="leftbar" class="leftcol">
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
</div>
<div id="centerbar" class="leftcol">
<h2>Section title</h2>
<div class="contbox">
<p>Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here.</p>
<p>Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here.</p>
<p>Contents for center column go here. Contents for center column go here. Contents forcenter column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here.</p>
</div>
</div>
<div id="rightbar" class="rightcol">
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
</div>
</div>
<div id="footer">
<h1>This is the footer section of the web page</h1>
<p>Contents for footer section go here. Contents for footer section go here. Contents for footer section go here. Contents for footer section go here. Contents for footer section go here.</p>
</div>
</body>
</html>
If you take the time to study the CSS styles attached to the previous web document, you’ll see that there is a declaration that incorporates a “bg.gif” GIF image into the corresponding “body” selector. In this way it constructs a gray background that’s tiled across the X coordinate of the document.
Of course, if you're used to building web sites, this process must be extremely familiar to you. So let me show you how the gradient looks with the following screen shot:
All right, I taught you two traditional approaches for building a faded gradient using both JPG and GIF images. However, suppose for a moment that you wish to achieve the same effect on your web pages with a PNG graphic that starts with a smooth gray color and fades progressively to transparency (remember this characteristic is called alpha-based transparency).
In this case, the gradient in question could be created by specifying the aforementioned PNG as a background image, along with a solid color. Simple, isn’t it?
Naturally, the biggest issue to address here is the lack of native support from IE 6 for transparent PNG images. However, as I expressed in the introduction of this article, it’s possible to implement a simple CSS workaround that will allow you to build the same gray-colored gradient that you saw in the previous hands-on examples using a tiny, partially-transparent PNG graphic.
Actually, I’m getting ahead of myself, so please read the following section, where I’ll show you how to build the web page background for non IE-based browsers.
Style Sheets 
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HTML5 Boilerplate Introduction
