As you can see if you click the link below, I have 2 validation errors in my CSS. I wanted to decrease my opacity in my drop down menu a little bit, but apparently it's not valid in CSS 2.1, but a later version.

W3C CSS Validator results for (CSS level 2.1)

Is there some kind of DOCTYPE for this? Sorry I'm still new to this.

By the way, ignore the warnings. They were done on purpose.