HTML is getting pretty old now and we have all learned the ins and outs of it. There are a few things we have learned so far.
Never, ever, use the font tag. There really is no excuse anymore for using it.
Do use heading tags, such as h1,h2,h3,h4. Also use them in the correct order like below
<h1></h1> <h2></h2> <h3></h3> <h3></h3> <h4></h4> <h3></h3> <h1></h1> <h2></h2>
The title tag is still very important. Do not have the same text for your entire site. Allow the title tag to change on each page. Also have some sort of order similar to crumbs in your title tag.
Always, always use a DOCTYPE. If you don't, you don't deserve to be a web designer. Without it browsers go in quirks mode and render your webpage however they feel like. Kiss that css layout goodbye and forget about the :hover psuedo class.
Disable your css often. It helps to turn off your css and see what your site looks like under the hood. Is the information presented in a logical way? Are important items still looking that way? Are you using lists for items that are grouped into the same context? The first thing I do when visiting new websites is disable the css to see how much effort they put into their design.