Why are locked up Internet Explorer pages so hard to terminate in Task Manager?

Sometimes Internet Explorer web browser pages will lock up and cannot be clicked on to terminate. So I do the usual ALT-CRT-DEL three finger salute to bring up the Task Manager. Click on the offending IE pages to kill them and they keep popping back up, and popping back up, and popping back up after you click on them to kill them.

What is going on? Why can’t the Task Manager just kill them. Why is it like playing Whack a Mole until the page finally dies after about the 10th time killing them?