Validating your website
Hacks for specific browsers (I’m looking at you Internet Explorer) also won’t validate, though it’s unlikely you’ll find a developer who’s never written a coding hack.Sometimes they’re all you have to get the page working right.Some of those warnings aren’t going to be things you’ll want to fix.Many tracking parameters you add to the end of a url will give a warning for example.
Much as different languages have different rules of grammar, the code you use can have different rules depending on the doctype you use.The home pages of Google (35), Yahoo (167), and Bing (14) all have validation errors.However all things being equal I would think valid code better for search engines than invalid code.Sometimes when you run a page through a validator the list of errors seems so large that it looks like it will take days to fix them.Often a few simple errors are leading to many more.
Search for validating your website:
Validators will also issues warnings in addition to errors.