my hp laserjet 6l does not give correct print

what kind of error?? a smug that on the paper in the same spot?? if it is there somthing on the image drum of the toner. if the image is off centered it could be the paper or an alignment issue with the laser. if it print fine on the paper but your getting junk..start with booting your pc into safe mode and uninstall the hp printer drivers and reinstall the newest drivers. check that the printer cable not damaged. try a factory reset on the printer in case someone changed a setting on you.