The link below has information for beginners, intermediate and advanced - a complete Web Developers resource. You are unlikely to need more than one GOOD source for HTML advice and help - this could be it:  Web Developers Virtual Library

However, if that one site is not enough, or you want to go beyond simple HTML, here are some more useful sites.

The first is a really helpful starting point for using CSS. You really should be looking at CSS instead of Tables for page layout. (I know, I have not yet reverse-designed this site completely back to CSS, but a lot of unnecssary tables have gone.)

Floatutorial - step by step guide

For more help on CSS, just put "CSS help" into Google.
Or buy a book or two from these great teachers: Sitepoint

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XML101