Do not move things right before I click on them.
Windows this means you. Opening up a new window steals focus from my mouse to the new one. Opening a new window when I did not explicitly request it and while I am typing or navigating something in order to do something critical infuriates me.
Facebook this means you too. Adding new comments to the Newsfeed a tenth of a second before I click on a comment box means I click on the wrong one. It is the kinds of thing that will drive people like me to Google+.
My coworkers will thank you too for me not discovering creative new obscenities to describe your products.