Observe that the jQuery UI CSS does not pass validation.

I try to adhere to standards wherever I can find them. I'm looking at jQuery UI and wondering why a group of developers that makes a solid product doesn't seem to even acknowledge the W3C-imposed standards.

Is the W3C CSS Validator just too picky? Or should I pay better attention to these errors/warnings?

Is valid CSS important to adhere to? Why do you feel it's important?

css validation standards w3c
Edit
Report