also...there are both programs AND web pages which will look at your page and analyze it for HTML compatability...and make suggestions...(I don't have the web page handy right now...but....

One program is Arachnophilia, which has a feature called 'beautify'...with subcategories of 'analyze', 'compress', 'beauitfy HTML', and 'beautify code'

the program is freeware, and now exists in a totally rewritten JAVA format, but is still available in the standard format for those who don't wish to install JAVA yet....

look at http://arachnoid.com/