[css] is there any IE8 only css hack?

There are various ways to get a class onto the HTML element, identifying which IE version you're contending with: Modernizr, the HTML 5 Boilerplate, etc - or just roll your own. Then you can use that class (eg .lt-ie9) in a normal CSS selector, no hack needed. If you only want to affect IE8 and not previous versions, put the old value back using a .lt-ie8 selector.