Have spent far too many hours this week trying to get IE6 to allow a <div> tag to scroll nicely. It worked in an HTML page written by hand, but not in the equivalent generated by a .NET 2005 aspx. The difference was all in the very first line:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
Took this out of the aspx and it worked fine. Doesn't work in Firefox or Netscape though.