I tested it in IE8,anf fierfox,and I have 2 remarks:
- the rounded corners dosn't work on IE, you can use IE pie to resolve this problem
- the bubble also dosnt work on ie, I tried this effect in a website I did from few months ago, and I faced the same issue in ie, and after looking for a solution, I found that the js file contains an error in hard-coded sizes to variables, I change them and this is my js file, maybe it will be useful. I am sure it working well