The Joomla Template Style Sheet is usually called template_css and is situated in the joomla template folder.

This contains standard css information which relates to all of the images, tables, divs, tds etc used in your joomla template layout file.

An example of a Joomla Tempalte CSS is shown below:

a:link, a:visited {
text-decoration:none;
}

a:hover {
color:#000000;
text-decoration:none;
}

div.moduletable h3 {
color:#333333;
font-weight:bold;
margin:0pt;
padding:0pt 0pt 7px;
text-align:left;
text-transform:none;
}

td#sidenav div.moduletable {
padding:0pt 5px;
}

Each Joomla template css file will contain particular css information relating to that template design.