You could do it through the use of FRAMES.
For example your intial page could have the following:
<HTML>
<HEAD>
</HEAD>
<FRAMESET ROWS="100,*" FRAMEBORDER="NO" BORDER="0" FRAMESPACING="0">
<FRAME SRC="empty.asp" NAME="banner" MARGINHEIGHT="0" MARGINWIDTH="0"
SCROLLING="NO" NORESIZE>
<FRAME SRC="home.asp" NAME="main" MARGINHEIGHT="0" MARGINWIDTH="0"
SCROLLING="AUTO" NORESIZE>
</FRAMESET>
<NOFRAMES>Your browser does not support frames. You need a browser
that supports frames to view this site.</NOFRAMES>
</HTML>
Then in main frame (home.asp) you could call an onload function which
changes the banner frame (empty.asp) to the new desired banner.
<HTML>
<HEAD>
</HEAD>
<SCRIPT LANGUAGE = "JavaScript">
var runMe = runScripts();
function runScripts()
{
parent.banner.location="banner.asp";
}
</SCRIPT>
<BODY>
Your main page.
</BODY>
</HTML>
So effectively you have 4 pages:
default.asp - the framed page
empty.asp - the empty banner page
main.asp - your home page
banner.asp - the slow advertising page
Note: The pages do not have to be asp!