Road markings usually come in three colours; yellow, red and white. Most yellow road markings prohibit you from stopping or waiting. Most white road markings are there to guide you safely along your route. They assist you with your positioning on the road and help you establish your priority in relation to other road users (i.e. at junctions). In general, you should never cross a broken or solid white line (whether in front or at the side of you) unless you have carried out the M-S-M routine first and checked that it is safe to do so.
Red markings are usually areas where drivers should avoid for instance in a cycle zone close to traffic lights.