hi guys! well i don't know if my doubt is a css thing or javascript or php lol
but i want to have a page that "asks" the user what resolution he's using and show a background according to that resolution

so.. i thought for that i need to make background with diferent dimensions

800x600 | 1024x768 | 1280x800 | 1280x1024 | ....

anyway how can i make that?