Website Building.. My CSS File Dosent Work When Uploaded?

Hi guys, was just wondering if anyone know what is causing this problem... I Build a website and saved it, there is a css file that turns the content slice into a background to put text on top off, This is the Css Code. It works when i open the html file from a local folder.

#content {
background-image: url(%5Cimages%5Cindex_21.gif);
background-repeat: repeat;
text-align: center;
}

But when i upload it to my webhost the image dosent show up. The place where it should be is just blank.

And here is the code i put in the html page where the background should be..

<td colspan="11"><div id="content">
<p> </p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p>s</p>
<p> </p>