It can be easy to make a mistake, like forgetting a tag, that can mess up your entire page. Typically, this happens thirty minutes before your client is due to arrive to see the final page. Frantic searching can solve the problem, but it's often easier to use a validator to correct the problem. There are many types of validators, make sure you find the one that works the best for you.
Muti-Purpose HTML Validators
Most multi-purpose validators are online - and they do much more than just validate your HTML. These tools will check your links for bad links, spelling errors, download time, and more. If you're looking for a "one stop shop," these validators may be perfect. They are easy to use, and cover the issues you might have with your Web site. Sometimes multi-purpose validators are hard to understand.
Online Validators
Online validators offer an easy way to check pages that are already live. You simply paste your URL into the Web form, and receive the results, either on the Web or by email. These validators will only work on pages that are publicly accessible on the Internet. If your page is not published, or it's behind a firewall, you'll need a different validation tool.
Browser Emulators
I strongly recommend that you check your Web pages in as many Web browsers, versions, and operating systems as you can. But sometimes this is not possible. Luckily, there are browser emulators available so you can see what your Web page will look like in browsers such as MSNTV and AOL. You can also see how your page will look in different HTML versions.
Link Verifiers
Link rot is a difficult problem on Web pages. The more links you have, the more likely that every day one or more of them will go bad. Using a link checker regularly is an important part of site maintenance. But they are not 100% accurate. Don't be surprised to find broken links that aren't caught, and non-broken links that are listed.
Other Validation Tools
It is also possible to validate the spelling and grammar on your Web pages. You can also use tools to check how accessible your pages are. CSS can be validated with various tools. Finally, there are validators and validating parsers for your XML documents as well.
