Often a few simple errors are leading to many more.

validating cancel true-37

You can click any of the 3 images for a larger and readable image.

Note that I also left off the period after “This is a sentence” above, which violates the rules of grammar, but likely doesn’t cause any problems in communication.

Browsers won’t care much either as they’ll typically render much invalid code perfectly fine. Still there are good reasons to validate your code.

The only people likely to care or even know how to check are fellow web developers. The W3C offers 5 reasons for why you should validate your code. Valid code is more accessible as it’s compliant with standards.

For example This is a sentence validates under html 4.01 transitional or html5 where the closing tag is not required, but not under xhtml 1.0 transitional where the closing tag is required.

I’ve included some screenshots at the bottom of this post to show the full code I used to check under each doctype.

Click the More Options link to see on each page to see.

There are plenty of browser extensions that will test the page you’re viewing in the W3C validators.

Since validation is comparing your code to W3C standards I think the best way to validate your code is using the W3C validation tools.

If you click the links above it’ll look like they go to the same page, but I assure you they’re different.

Some will probably tell you that valid code will help your pages rank better. Other than show stopping errors (which validation can help you find) search engines really don’t care much about your code.