I typically use http://validator.w3.org/ to check my sites for valid HTML. With so many new features, it is sometimes difficult for the validation to keep up. For example, I am using picturefill.js for responsive images. As a result, I see a lot of this in my validation report:

Element img is missing required attribute src

So, is validation useless? I don’t think so. I still look through the report to find “real” errors such as unmatched tags .