If you pay someone to build a site, you should at least write into the contract that they use valid HTML. An easy way to tell whether your site will work on a variety of current and future browsers is to use the validator from W3C:

http://validator.w3.org/check?uri=http%3A%2F%2Fwww.qatarhappening.com

Another problem with the site is that it's using some really poor javascript to do the scrolling text and rollovers. I don't really like that sort of thing, but if you're going to use those effects, you should use javascript libraries that have been thoroughly tested and debugged, such as jQuery or Prototype.