MediaWiki:Common.css

/* CSS placed here will be applied to all skins */
.catlinks
{
display:none !important;
}

#catlinks
{
display:none !important;
}

p.catlinks {
display:none !important;
}
 

.catlinks ul {
  list-style-type: none;
  /* ... */
}
.catlinks ul li {
  /* styling for the single items */
}