I'm trying to create a print CSS file for a university assignment. Part of my CSS is:

```
#footerRight a:after {   content: " (" attr(href) ") ";}

```

On the page it works fine. Definitely prints the href where it should. But the CSS won't validate. Errors I get are:

```
#footerRight a:after    Parse Error attr(href) ")";
#footerRight a:after    Parse Error }

```

I also tried a:: and a[href]: as a couple of blog posts I found suggested, but still it won't validate.

Any ideas? Sorry for the beginner level question.

Jackson