Welcome toCleaning.Tips.Net
Subscribe to the Tips.Net channel:

Visit the Tips.Net channel on YouTube
ExcelTips
Organizing Tips
Pest Tips
WordTips
Removing Tinsel from Carpeting
Removing Pine Needles from Carpeting
Properly Disposing of Gift Wrappings and Packaging
Removing Hard Water Stains from Fiberglass
Removing Hard Water Stains from Linoleum
That blue sticky stuff is known as either PresStick or Blu-Tack, depending on where you live, and is made by the Bostik company. This is some of the most wonderful stuff that people have at their disposal to hang up light pictures and posters without leaving those nasty holes that are common to most college dorm rooms. Until it is time to move those pictures that is. There always seems to be a little of the substance left behind, and usually the longer that the stuff is left there, the more of it there is. Well, here is how you can clean up that mess and get on with your life.
To start, it must be noted that on the official official Bostik website it states that the adhesive qualities of Blu-Tack increase with time and that extra care must be taken when removing the substance from the walls as it may result in removing paint as well. The best way to remove the adhesive is to roll it off gently, using a larger piece if any is left on the wall. While the corporate website recommends using either lighter fluid or dry cleaning fluid to remove any residual stain, I would recommend that a citrus-based stain remover be used instead. This way there is not the risk of soaking a wall in a flammable substance that could lead to a different problem later on.
If the substance has been left on a painted wall for a significant amount of time, the removal of the Blu-Tack can create a different problem. Unfortunately, the more time since a wall was painted, the more porous it becomes. What this means is that the porous wall can suck out the oil from the Blu-Tack. The end result of this is that it could discolor the paint to the point that it is ruined. If this happens, there is no way to fix that discoloration short of repainting the wall. It is my recommendation that in order to avoid this difficulty, you rotate your picture locations periodically. In addition, it may be a good idea to repaint your room every so often. Of course, the most economical solution may simply be to use thumb tacks to hold up your pictures in the future.