Use Photoshop Save for Web. . .these settings are typical of most image editing apps.



Thumbnail size (weight) cannot exceed 15K, file dimensions must be less than 212 x 212
pixels.

If you don't have a compression program:

Try Thumbnail wizard here: http://www.jpegwizard.com/thumbn/thumbn.asp

For Full jpeg resize go here: http://www.jpegwizard.com/

For an excellent (free) image-handling program I recommend IrfanView
http://irfanview.com

Use Internet Explorer for uploads – Netscape seems to try to change the default thumbnail
size and handles scripting poorly.