Replace presentational tags with structural markup
You can use find and replace (and regular expressions), but the easiest way to do it might be to view your existing page in a browser and copy and paste the text from there into your HTML editor.
Think about the structure of your document! Merely replacing
<b> tags with
<strong> tags is not enough.
What is the most important header? Mark it up with an
<h1> tag. Mark your subheads with
<h2> tags and so on. Mark up paragraphs with
<p> tags. Mark up your navigation as unordered lists.
DOCTYPE and use it. (We recommend XHTML transitional, unless you're hard core, in which case, go for it and use XHTML strict.)