Background colors do not show up in certain browsers, i.e. netscape. Is there any way to work around this?

They should show up.
Can you post the code that you're using?

They should show up.
Can you post the code that you're using?

<style type="text/css">

body
{ margin-top: 0;
margin-bottom: 0;
margin-left: 0;
margin-right: 0;
padding-left: 0;
padding-right: 0;
}

#header { width:100%;
margin: 0px;
padding: 0px;
height: 5%;
background:FFFFFF;
}
#left {
position: absolute;
left: 15px;
top: 100px;
width: 5%;
}
#center {
top: 0;
margin-left: 5%;
margin-right: 5%;
height: 90%;
background: 000000;
}
#right {
position: absolute;
right: 15px;
top: 100px;
width: 5%;
}
#footer { width:100%;
margin: 0px;
padding: 0px;
height: 5%;
background:FFFFFF;
}

A:link
{ text-decoration: underline; color:#AAAAAA; }
A:visited
{ text-decoration: line-through; color:#AAAAAA; }
A:active
{ text-decoration: none; color:#AAAAAA; }
A:hover
{ text-decoration: underline overline; color:#AAAAAA; }

</style>

Shows up in IE and AOL, but not on netscape or firefox.

Instead of:
background:FFFFFF;
Try
background-color:#FFFFFF;
Repeat that for all your other background colour codes.
And if this is an external stylesheet, remove the beginning/end style tags.