[stomachmonkey]

Trackpad could be going. Hook up a mouse and use it exclusively, see what happens.

Trackpads sense heat.

Do you wear a watch or bracelet? Sometimes a piece of dangling jewelry can pick up enough body heat to trigger the trackpad.

Trackpads don't like wet/moist fingers.

Does it happen in every application? Start up Wordpad or something else that takes text input. When the browser acts up switch to the other app and see if the problem persists. Or download and try a different browser.

Clean the keyboard by gently vacuuming it. Don't blow compressed air into it.