Test HTML of a website maintains w3 standard or not

It is necessary to test whether HTML of your website maintains standard of W3 or not. To test that you can try any or more than one ways described below. First one is validator of W3. This validator tells your errors of your websites. This validator can be found on http://validator.w3.org/.
You just enter domain of your website on the address bar and click check. Then this validator shall tell you errors of your website and also suggestion.


  You can also try HTML Tidy which is described in these words, "HTML Tidy is a free utility for fixing HTML mistakes automatically and tidying up sloppy editing into nicely laid out markup. It also works great on the atrociously hard to read markup generated by some specialized HTML editors and conversion tools, and can help you identify where you need to pay further attention to making your pages more accessible to people with disabilities."
You can use Amaya, an open source product (huge opens ource software to download and use), is both browser and hypertext editor. It's a test-bed for the design of embedded math, objects, stylesheets, structured graphics etc. If your website can viewed without flaw, then it can be viewed perfectly in all popular web browsers. You can also edit your website through this software.
You can find more validator tools on http://www.w3.org/QA/Tools/