anyone help with this? i installed add-on maps before it titled urban flight and it was working when another map i installed it goes with that idont know letters but i deleted that mod and the problem is ... it still the same even i deleted that shit corrupted mod anyone help???

The mod problem was a virus, or the map took up a lot of hard drive space, and, because when a game runs, it uses hard drive space, so that's probably why. Also, make sure it is fully gone. Just because you put it in your recycle bin does not mean it's gone. Go into the recycle bin, right click on it, and click on "delete".

it still the same

try verifying the cache of the game

It looks like it'd be worth deleting your addon.txt file. (make a backup first)
It's in (something like) C:\Program Files\Steam\steamapps\common\left 4 dead 2\left4dead2

If you don't see it just run a search. Run the game and see if that helped.