If you are going to try to learn HTML, then you should learn XHTML. There are many old ways of doing Web Design that are no longer valid. At least 40% of every web design book will be about stuff your not supposed to do. Just skip those chapters on Frames, Deprecated Tags, and Layouts with Tables.
Once you learn the right way to do it, you should validate your site. Just go to http://validator.w3.org/ and enter the full address of your web site. Then you can put one of these pretty logos on your site.
It basically says you are a Wizard of Web Design.
Explaining the differences and geneology of SGML, HTML, XML, and XHTML would take too long. Fortunately this is a topic that is addressed on several thousand web sites. Research on line or buy a current book to learn more.
If you are looking to hire a web designer, putting one of their sites into the validator would be a good way to see if they are 'up to code.'