*The banner is an image link, so if you don't set separate styles for it, it will be affected by image link styles.

Make It Disappear
<style type="text/css">
.maintop img { display: none; }
</style>

Borders
To put a border around the banner (this code makes the border change on mouseover too):
<style type="text/css">
.maintop a:link img, .maintop a:visited img { border: 1px solid red; }
.maintop a:hover img { border: 2px dashed green; }
</style>
[ More Border Styles ]

Background
To set a background color for the banner (color changes on mouseover):
<style type="text/css">
.maintop a:link img, .maintop a:visited img { background: deeppink; }
.maintop a:hover img { background: orange; }
</style>
(Nb, if you just want to get rid of the annoying little purple bit on hover, just set the hover background
color to match your page), ie:
<style type="text/css">
.maintop a:hover img { background: black; }
</style>
More on
[ Backgrounds ]

Image Filters
To apply a filter to the banner:
<style type="text/css">
.maintop a:link img, .maintop a:visited img { filter: fliph; }
.maintop a:hover img { filter: flipv; }
</style>
Nb, filters only work in the IE browser, except for
[ Opacity ] which is cross
browser.
[ More IE Filters ]

Positioning
To move the banner to the left or right, just float it like this:
<style type="text/css">
.maintop img { float: left; }
</style>
If you want to create a space above or below it, or just move it a teeny bit left, or right, you can
use margins, for instance, this code would move it just slightly to the right:
<style type="text/css">
.maintop img { margin-left: 100px; }
</style>
And this one would create a space around it, top and bottom:
<style type="text/css">
.maintop img {
margin-top: 20px;
margin-bottom: 10px;
}
</style>