Periodically people will try to argue about should they have valid HTML for their websites. Some argue that you should always validate.
But does it really matter?
Imagine a web browser that could only view valid HTML websites. What would it view?
We’ll I’ve read in times past that over 80% of all web pages have one or more errors on it – yet almost all of those pages can be read by a web browser.
Would you use a web browser that could only view 20% of the web, at most? Of course not! Web browsers, and the spiders that search engines use, are notoriously good at figuring out those errors, and fixing it so it can read the web pages.
So while valid HTML is extremely important as it will make display faster, make your code more maintainable, and easier to hand off to other people, it isn’t something you should overly worry about if you can make the page appear in your major browsers correctly.