The element.innerHTML property
This topic is an advanced technique for the website tempusfugit.me.uk, please read this page with this in mind.
W3C say:
Security risk
The MSN website discusses this in more detail. The suggestion is that you use ????? instead of innerHTML. MSN also say that your code is likely to be rejected if it is submitted for review to Mozilla.org for inclusion into an addon. This does not apply to me.