With all the changes I have made to the code over recent weeks, one thing I had forgot about was keeping the code valid, until that is Tony the managing director was having a look at the site and clicked on the valid xhtml button at the bottom of one of the pages and it failed. So after 10 minutes testing each page and making a few small changes to the code the site is once again xhtml 1.0 valid, it seems that as I was removing old code I left the odd tag behind which didn't affect the site in the latest browsers but could have caused a few problems with older browsers.