It's good practice to have your site checked for conformance to HTML standards and syntax. An informal way to do this is to obtain several web browsers (Netscape, Mosaic, Internet Explorer, etc) and see how the appearance of your site changes with different browsers (and different versions of the same browser -- because not everyone uses the latest browser version).
The most reliable approach to checking your site is through a validation service. Here's the best:
NOTE: When you submit your pages for validation, you will get varying responses depending on which HTML standard is applied. For example, if you request validation by the HTML 2.0 standard, and your page has items (tables, image ALIGN attributes, <CENTER> tags, and a few others) that aren't included in HTML 2.0, you will be told that your page has errors.
To know what standard of HTML to apply, validators take their cue from the DOCTYPE line at the very top of your file. Most of the pages in this site follow HTML 3.2, and have the following DOCTYPE line:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">This DOCTYPE line tells the validator that the file has been marked up according to HTML 3.2 (English version), as promulgated by the W3C (World Wide Web Consortium).
Incidentally, validation services are automated computer programs, something like the "debuggers" that programmers use. Don't be embarrassed to submit your pages before you think they're perfect. There's no charge for these services, and there's no one sitting there making fun of your learning process...