The problem just suddenly existed few days ago i dont know what i've done. Whenever i scroll page up or down using mouse wheel, the page just keeps scrolling up and down at the same position. Like when i scroll down 2 lines it scrolls up maybe 3-4 lines then down 1-2 lines again. tho eventually it does go to the line i want if i keep scrolling but this is annoying and really dizzy watching the page up and down. is it the problem of the mouse itself (i havent tried with another mouse, this is a new mouse i use it for a month only) or system? how to fix it, any idea??

Check mouse settings in Conrtol Panel. There should be a setting that determines how many lines are scrolled for each click of the wheel. If the number is set to more than two or three, it seem erratic because you can click faster than the system can react. I like to keep the setting to 3 (default) or less. If this isn't the problem, you could have a defective mouse. -- kptech