I have a webpage and a CSS file for it.My problem is in the CSS file when I am using

@-moz-document url-prefix()

On my computer the CSS rules apply but on anothe computer it does not work(tested with same version of Firefox) which is really odd. Here is my exact CSS code if that helps in any way:

Code:
@-moz-document url-prefix()
{

  .SelectStyle {
    position:relative;
    top:-17px;
  }

}

.SelectStyle {
float:right;
}
Am I missing or doing something wrong here?