Hi Laney,
The maximum allowed size for avatars are 85 x 200 pixels. The avatar does not have to be square (mine isn't) but it has to be jpg.
If it is any
help my avatar is 0.84 X 1.3 inches at a resolution of 96 pixels
per inch. it takes up about 3.00KB.
Unless something has changed it shouldn't make any difference whether you are using Internet Explorer or Chrome, but I mostly use Chrome and Firefox myself and there may be a problem with Internet Explorer that I'm unaware of.
*Alex.