What is the best (or very good) HTML Validator for Windows? I know of http://www.htmlvalidator.com but it isn't free.

What about this?
http://validator.w3.org/

That's my favorite

Yes, that is very good... But I am looking for software for Windows...

I'm assuming for free.

If you find a free one do let me know. Though w3 validator is pretty much on the money

I don't think there is any specific software. You can get a Firefox addon called HTML Validator which uses almost the same protocols as W3C does, but that's as close as you will get unfortunately, and given that W3C is the HTML validator, you should be using that over any other.

You could always download the W3C source code and run it locally, but it's very hard to setup. Ubuntu offers an easy option to install it though, but the repository is out of date.

Webdeveloper Toolbar of Mozilla Firefox addon.

What's wrong with using http://validator.w3.org/ ? It's free and full featured, all you need is a Web Browser

CSE HTML Validator Lite
http://download.cnet.com/CSE-HTML-Valid ... tag=button

Use http://validator.w3.org/unicorn/ which validates HTML5 as well as CSS3 as well.

There is a Chrome extention called Validity for Google Chrome, i tried it and its working pretty good you can get it here: https://chrome.google.com/extensions/se ... q=validity

One site I like to use also is this one http://browsershots.org/ where you can see what your website looks like in many different browser. It's interesting to see how some of the oldest browser behave.

I cannot think of a reason why you schouldn't use the W3C validator. But, if you really want software, your best choice is probably a plugin for Firefox or Chrome.

I've got to side with everyone else and vote for the W3C Validator. The only reason not to use it is if you're developing pages whilst offline, which seems counterproductive if you're testing a webpage in a production environment.

What about HTML Tidy (http://tidy.sourceforge.net/)?

It not only reformats (i.e., tidies) HTML, it can also be used to validate it.

Try this one: http://html5.validator.nu/?doc=<domain here>&showimagereport=yes&showsource=yes

With this options the comments will help you

I use the Web Developer addon for Firefox 4, as it has convenient options in the Tools drop-down to validate pages using the validator at http://validator.w3.org/. It has a normal button to validate the HTML by the URL on the internet, but even local HTML can be validated, with the validate local HTML button. It also has buttons to validate the CSS and such.

The w3c validator is the best out there, me being a web dev it has saved me many times, I prefer not to use software due to the slow updates that they have... Plus if the w3c changes it instant notification...