If it is on all webpages, does it work just on your desktop?
If not check your mouse settings in control panel/Mouse.
Or your mouse could be damaged.
If it is only on a couple of webpages, it's most likely the coding of
the page itself. Try using Firefox. It doesn't always allow the same
scripts to run.
Because it doesn't work on your desktop either. I'd check your mouse
settings, in control panel.
If nothing helps there. Check to see if your mouse is a usb connector
plugged into the PS/2 jack, try using it as a usb mouse. Otherwise test
your PS/2 socket with a known working mouse. If that mouse does not
work, your PS/2 socket could be corrupted.