What addon was it?

[Efx]

I had downloaded a random ui a while ago, and it had one little addon that was splitting the screen into little squares/lines or something, so that you could position/center the interface's elements.

Any clue what I'm talking 'bout?

[Soulofsin_007]

http://www.wowinterface.com/download...53-Align.html?

[jeffy162]

Align. Looks like the last update was 08/05/2009, but I use it and it still works fine. If you're really picky about lining up your UI elements, you could also use Lineem Up. Also a bit out-of-date, but still works fine.

[Seerah]

There is also GraphPaper.