what would be the average size for an avatar??

100x100 - Forums.
48x48 - AIM.
100x100 - MSN.

:]

^yup.
except some forums only allow 64x64..
but not Cb..

and what about yahoo? I'm too lazy to look, can anyone tell me?

so would i use 100x100 for xanga?

Yes. But Xanga allows pictures up to 160x160. 100x100 is merely the average size of an avatar.
There's also a code provided in Xanga Scripts that will allow you to have any size avatar, so you're really not limited at all.

48x48 on AIM? And I've been using 50x50 all these years...*bangs head on keyboard* Does it cut off the extra pixels if you do that?

No. 50x50 is just the max size. I use 50x50. 48 just insures that it'll fit.

48 for aim also always shows a border if you put it on there.
i used to use 50x50