Chrome Dev Tools has a built-in :hover state selector in the Elements > Styles panel. You can toggle other pseudo-classes (like :active) there as well.
Also in Firefox, if you want to debug the DOM instead of the CSS, you'll have to : 1) press F12 to open the inspector 2) select the Debugger tab 3) hover the element you want to inspect while in the :hover state 4) press F8 to pause the debugger 5) select the DOM Inspector tab Everything stops while in pause mode, JS, DOM refresh, CSS states, but CSS animations. The most important is to be in the debugger tab while pressing F8.