I found nasty
*improvements* in java script engine

Suddenly some of my favourite web sites runs slower and some web link does not work.
I found what happened by comparing the same page on notebook. There are advertisement embeded on the page which pop-up at some time. On iPad with 4.3 they also popup but unvisible so you cannot close them and obviously the javascript blocks somewhere in infinite loop of advertisement animation which never appear. I just pushed my finger for a longer time and blue "copy" box highlighting the invisible advertisement showed. However there is no way to close the invisible window. That's real bug in the new javascript engine.