confusing icon

[alfonso.garcia]

I cant seems to get what this icon ( the one in my avatar ) is for and what it represents, or how to turn on or off.

Not sure if its iOS5 specific, but seen it on many iOS5 screen shots.

thx in advance.

********* update:

avatar didnt work: here now http://cl.ly/2j1I1W2m0o3D030b2L3Q

 

[anim8or]

Its the screen rotation lock... its been around since iOS 4 i think... its left of the first page on the Multitasking panel....!