In MediaWiki there are two preferences: "Disable AJAX suggestions" and "Enable enhanced search suggestions (Vector skin only)".
They are problematic for several reasons:
1. Most average users don't know what AJAX is. It should be just called "search suggestions".
2. The first option says "Disable", but the second one says "Enable". It's confusing - both should say "Enable". "Disable AJAX suggestions" should become "Enable search suggestions", and the value of the checkbox must be reversed for all users.
3. Better yet, the two options should be merged into one. "Disable AJAX suggestions" doesn't seem to do anything useful in Vector, no matter whether it's checked or not, and "Enable enhanced search suggestions (Vector skin only)", as its name implies is relevant only for Vector. Separating them may have been useful in the early days of Vector, but now that a year after the rollout Vector is rather stable, this doesn't seem to be useful any more.
-- Amir Elisha Aharoni · אָמִיר אֱלִישָׁע אַהֲרוֹנִי http://aharoni.wordpress.com "We're living in pieces, I want to live in peace." - T. Moore