With WebKit Nightly, my user stylesheet is ignored, but with the current version of Safari it is applied. My user stylesheet contains the following: textarea { font-family: Monaco !important; font-size: 16pt !important; color: green !important; background: black !important; min-height: 50pt !important; } An example of a page this happens on is this bug report form itself.
<rdar://problem/6533039>
Works for me after a restart of the browser. If I remember correctly, it used to work without restarting.
It works for me too on restart of WebKit Nightly, but without restart with Safari.