You can use Acetone (not sure if it is correct in english). This solvent is the main ingredient of nail enamel remover. But use it carefully, if you wipe other stickers, you could remove them too.
boil your kettle, get some old bottle something like a spraymit or old window cleaner bottle and fill it with boiling water. have a sharp knife at hand and spray the sticker until its very wet and use the knife to peel one corner up until you can get hold of it with your fingers. now slowly pull the sticker from the frame whilst still spraying in between where the sticker is peeling and the frame. this really does work and does not damage the frame in any way. just make sure the water is boiling hot, after about five mins its no good so you need to keep the water boiling. use some turps to rub any left over glue on the frame. a word of warning though, if your frame is quite old you may end up taking the sticker off and being left with a shiny patch where it used to be, which means stripping the bike to have your frame polished. which could turn out to be expensive! good luck any way and mind your fingers, that water is hot!