This text will be green if the rule has been applied.
! #testElement {
color: #00cc00;
}
Combine this with one of Edwardson Tan's comment bugs and you have yourself a Safari 1.x / OmniWeb4.5 specific hack.
An exclamation mark is an invalid character in a selector so any associated rules should be ignored by standards-compliant browsers (so the text in the example block should be red in compliant browsers).
