If you want to see how your page holds up to HTML 4.0 standards (or anything lower), check out ZDNet’s HTML Check. It’s just an HTML form that asks you for your web page address, whether you want to check just a single page or your entire site, which standard you want to test with (HTML 2.0, 3.0, etc), and your email address. You click Submit, wait a couple of minutes, check your email, and they will have sent you a URL where you can see the results. The results will be there for 2 days, so you have time to fix stuff if you want to. Click here to see my results.
For example, on my page, it told me that some of the tags I was using are proprietary (only supported by one brand of browser), and that some of my HTML coding just wasn’t properly used. Check it out if you want your page to view exactly as the HTML standards say they should be.