These are caused by one or more of the print nozzles of an inkjet printer being blocked. The white lines are areas where no ink has been laid down. To fix things, use the head cleaning utility provided with the printer. This can be found within the printer control program, for which there is usually an icon on the right of the Windows Taskbar. If not, look in the Programs section ofthe Start menu under the name of the printer. To check whether cleaning has worked, use the nozzle checking facility in the printer control program rather than waste more ink on a reprint. The printer's manual will also provide a guide to cleaning nozzles.