Back then, Microsoft was forced (by some lawsuit) to require a mouse-click to activate each ActiveX control embedded in a web page, even Flash. This was implemented as an IE6 update, and also built-in IE7.
No need to explain why it's really annoying for users.. Ok, I'll explain anyway: think of an ActiveX control that contains buttons. Clicking the button first only activates the control, and another click is required for the button to be pressed..
Most sites used some types of hacks to overcome this.
So now Microsoft solved that law-issue (lots of $$$$s I guess) and they're about to disable the click-to-activate "feature" and bring everything back to the way it used to be, this time- legally.
However, there are already millions of computers with the "click-to-activate" IE version, and some of them won't install the update.. This means that I'll still have to use one of the hacks for the next few years. Annoying.