I guess (and with the poor information provided it's really just a guess) it might not be working because you are only using the vendor-prefixed versions of transform. The browser you're using might be already (and only) supporting the prefix-less form, so you need to add it:
-webkit-transform: skew(20deg);
   -moz-transform: skew(20deg);
     -o-transform: skew(20deg);
        transform: skew(20deg);
Oh, and if you're trying to copy the exact skew of the example you provided, only along the Y axis, use skewY() instead of skew() and 10 degrees instead of 20 degrees:
-webkit-transform: skewY(10deg);
   -moz-transform: skewY(10deg);
     -o-transform: skewY(10deg);
        transform: skewY(10deg);