Dunno if it has to do something with a quest or if it is just deco but under the bridge in whiterun the one at the gate where the guards house is, below it is a thing in the wall. some kind of symbol, has it a meaning? its just irritating me ^^

It's a shadowmark.

They're left by thieves to tell you whether a building has good loot, guards or is protected by the guild

There's more than 20 of them in Whiterun. Go look at all the buildings and some posts. I was initially mystified. The gentleman who answered is correct, however.

ah thanks so mucho that bugged me all the time ^^