Content aware CSS – apply style only if content is available

Simply use the :empty pseudo-class like so:

td.someClass:not(:empty) {
    /* Styles */
}

As Petr Marek mentions it’s not very reliable as a cross-browser solution, so if you must support older browsers (IE8 and older) you will need JS (which you can probably figure out yourself). Otherwise, the above CSS rule will work just fine.

You can find the browser compatibility of :not() and :empty here