Those shitty websites that don't let you leave!?

[TheDevilWearsPrimark]

No I'm not talking about mumsnet.

How do they do it, and why, I've been on two links today that force you to stay on the site until you ctrl alt delete. Why and how?

Don't know how they do it, but you can generally get out of them by clicking the down arrow next to your Back button & clicking on one of the entries on the drop down menu.