There are a multitude of different options to consider when designing web pages because of the variety of browsers, search engines and computer platforms that are available today, plus the iPhone, iPad, Android, etc. It's getting harder and harder to design a site that will be compatible with all of them. If people get irritated when trying to visit your site they won't come back and they especially won't refer you to their friends or associates or link to your page either.
Once you're finished designing your website HTML Validators will make that job a lot easier by letting you know if parts of your code will not work on some platforms and browsers. They will also check for broken links, image size, spelling errors and other problems that may not show up on your computer. However, re the spelling errors, some validators don't even know how to spell "validator" or "www" or "meta tag" so use your own judgment.
If your website has dropped out of sight in the search engines ranking then it might help to check your code with an HTML validator. If your website comes back in a few weeks then that was the problem. If not look for other problems such as Hijacking
