browser scrolling is not smooth

[boldenc]

Hi, what is the reason of the un-smoothness when scrolling the pages up and down, I notice little slow down, it is like random pauses when scrolling, and same pages could have this pauses and sometimes they haven't. I tried Firefox, IE, chrome and all will do the same. Maybe it is not noticeable for others but I notice it. Sorry for this noob question but I'm trying to know the reason is hardware or software.
Thank you and Merry Christmas for all

 

[boldenc]

At normal windows no, but when I open CPU-Z and try to move it, it will have jerkiness, though only happens when using windows 7 aero theme adjusted for best appearance. But still even when I use the classic theme, CPU-Z windows will not lag but still the scroll browsing is not smooth and it will have random pauses.