Dave,

you're an Admin, so you can see this information!

Go to the tab menu along the top of the page and click on STATS, then scrol to the bottom of the page and view Browsers and Operating systems.

You'll see the information there in a pretty graphic.

As of the time i'm writing this post;
Internet Explorer 10. accounts for (1.46%) of visitors or 34,210
Internet Explorer 9.0 accounts for (5.68%) of visitors or 133,521 - the most popular browser type amongst our visitors.