What do you mean by "disable" the admin dashboard, and why do you want to disable it?
I meen hiding the blue banner on all the special pages, because it annoys me. I never need to use the dashboard either.
It's not always blue (it varies based on theme designer settings) but I believe this would refer to the tabs admins can see at the top of pages like Special:RecentChanges.
Incidentally it could be done, but it's not completely un-useful. Something like
#AdminDashboardHeader { display:none; }
works, but there are side effects. Where I tested it the AjaxRC checkbox is mounted on the dashboard tabs, and vanished with the header. In short it can't be turned on or off without modifying the script somewhat (I don't know if this a standard thing or just the script used on the wiki I tested it on).
It also spills over to the admin dashboard itself (although there are ways around this) hiding the advanced/general tabs. Whilst advanced is basically Special:AllPages with some not-very-useable viewing stats general has links to Wiki features, Promote, User rights, Top Navigation (MediaWiki:Wiki-navigation) and so on.
So yeah, it can be done, but I wouldn't advise it.
Disregard the above CSS. Eladkse has made w:c:dev:HideAdminDashboard which does what you asked for far better.
Per Cam, that script does exactly what you ask. Please note it is for personal use only.
Hmm That's helpful. Seems weird that it's against the ToU, as it only actually affects admin's view of a wiki. The "Consistency" argument is also inlaid, as we have message walls and talk pages and Special:Forum and Forum:Index. Awell.
Kudos to you both, it won't let me do it on my iPod :P