I didn't ignore the previous mentions about IE having problems. I did lots of research and realised the problem is out of my hands. It seems that the problem lies with MathJax's ability to detect the correct browser with IE. MathJax has already added a number of (unnecessary) fixes for IE to work properly (the other browsers don't need this!). However, sometimes IE returns unknown values when scripts attempt to detect the browser/version and rather than waste any more time MathJax just gives up and displays the [Math Processing Error] error. If anyone has ever done web development they will know that since time began (in the browser revolution) IE has never played by the rules and it becomes necessary for web developers to constantly add random fixes for IE to work properly. Most web developers have given up now. They simply follow web standards and if IE doesn't render properly then it becomes clear where the problem lies.
The problem is that I can't fix a problem which I don't see, is not consistently reproducible, and/or is not resulting from bad code on the PE website; if anyone notices an error in my code then please let me know. Otherwise, the only constructive advice I can offer, and to anyone who is having problems with IE, is to contact the MathJax developers citing, say, the page for problem 505 (which is visible to all visitors), and asking if they can offer any suggestions as to why you're having problems. Of course, if I were one of their developers then the best advice I could offer would be to switch to a real browser.
