Couldn't Resolve Directory

I have a .tpl file, that has some HTML in it, that has some CSS in it. I'm trying to set the background attribute via the url() value in CSS. My URL is /icons/blah.png, and PHPStorm is unable to resolve the directory. Well, that directory is actually at http://icons.mysite.com/

Is there a way to tell PHPStorm that /icons/ URLs should go there? Maybe some way of mapping URLs?

Thanks!