[Mediawiki-l] Changing skin

[jaro]

Hi!
 Im trying to change the skin of my local copy of mediawiki 1.5.1. When i
enable this in Localsettings.php
$wgDefaultSkin = 'MySkin';
 I only get a plain text html in my browser. Myskin is only a copy of
MonoBook so im expecting to see something like the MonoBook. Then i look at
the source page and i found out its using the wikistandard css. Why is that
happening? What more do i have to do?
 I hope you can help me..
 -jaro