How many times have you come across a website that might look nice, yet annoys you with quirks, annoyances, or broken links? If you have a website (any who doesn't these days?), then you'll want to do your best to make sure that all of your visitors have a pleasant experience. You'll want to make sure your site functions smoothly, without errors and annoyances, and renders properly regardless of what browser your visitor might be using. On top of that, a little search engine optimization couldn't hurt either.
Addressing any underlying HTML, CSS, SEO, spelling, and broken link problems your website may have is a crucial first step toward a first-class, trouble-free website. A good automated website checker can easily find many of these problems, and even offer suggestions and solutions towards addressing them. Tools that can check many different aspects of a website with only one-click can be especially helpful and time-saving. Only after you've checked the underlying HTML & CSS should you move on to checking your site in different browsers, and then to user testing.
Also, be sure not to forget about accessibility checking. You'll not only help those who have vision disabilities, but everyone who accesses your site because the techniques used can often improve accessibility for everyone. Another benefit of an accessible site can be improved search engine optimization. For example, using keywords with appropriate image 'alt' text, is another opportunity to let search engines know what searches your website is targeting.
CSE HTML Validator is a tool that can thoroughly check a web page or website for multiple problems. There's a free online version at http://www.OnlineWebCheck.com. Just give it your website's URL and it will check basic HTML & CSS syntax, showing only errors and warnings. There's also a free (for personal and educational use) desktop version at http://www.freehtmlvalidator.com/, which offers basic HTML checking only, and then there's the paid version at http://www.htmlvalidator.com, which offers the most thorough checking, including CSS, SEO, link, and accessibility checking. However, you don't even have to pay for the professional version if you take advantage of the fully-functional, FREE PUBLIC BETA at http://www.htmlvalidator.com/freebeta, which lets you use a recent & fully-functional BETA version for free until January 31, 2013. For business websites, the paid version (or free BETA) is highly recommended.
And, for a limited time, save $25 when you buy CSE HTML Validator here, making the standard edition only $44. It's guaranteed to help you improve your site or your money back (30-day guarantee). Please note that CSE HTML Validator is for Windows only (except for the online version).