Yes, the w3 validator is a very useful tool. Sometimes, I find it a bit hard to understand, so I rely on the HTML Validator plug-in for Firefox. It uses exactly the same validation rules, but explains the errors in easier-to-understand language. If you have Firefox on your computer, you might give that plug-in a try. Can't hurt much . It can be found here: https://addons.mozilla.org/en-US/firefox/addon/html-validator/?src=search . If you are running FF 23, I recommend that you go to the author's site and download the latest version, 0.9.5.8 .
We always have to remember that perfectly valid code may not work. Even though all of the tags are correctly formed (and the validator smiles), the logic/layout may still be faulty. The validator is a first line of defense troubleshooting and quality control aid. I use it and it keeps me humble.
Glad to hear that the fix worked. Thanks for the feedback.