Unknown pseudo-element or pseudo-class :hover

I've never really paid this close attention but I'm getting the following error:

Unknown pseudo-element or pseudo-class :hover 

on the following code

A:hover { COLOR: #F56655; text-decoration: underline; 开发者_如何学Go}

Since when has :hover not been valid css and what is the alternative?

I have seen this used everywhere...

Double check your validation rules, testing here I get no errors, using CSS 2.1:

http://jigsaw.w3.org/css-validator/

If you're testing CSS 1.0 compliance, you'll get your exact error, since :hover wasn't in CSS 1.0, it was added in 2.0.

I believe it's just your capital A, use a lowercase and should be fine.