Good call Namun - using !important is very handy sometimes. For the OP: !important makes it so that the attribute overrides all other CSS. Of course, using !important is kind of bad practice - it usually implies that your code is poorly organized and that you have overlapping CSS rules. CSS should inherit - not overlap.
And in my experience, when people start using !important, they start using it everwhere... which gets even messier.
Just fyi: if you have more than one !important effecting the same attribute, the first one overrides the later ones (so the order in which your css is included/interpreted matters).