Well I am not a iphone guy so not real sure how it works with one. On my Android I have a crop or a resize function in the edit area of a picture.
On my computer I use the simple Microsoft paint software. If you open with paint on the menu bar you have a resize option. All you have to do is change the percentage size in the Horizontal and Vertical boxes from 100 percent to say 50 percent and it will automatically resize pic for you. If your still not sure how big it is you can resave it and then right click on it and go to properties and it will show you the new size of the picture.
If I remember correctly the forum only allows up to 10 pics or 2 megs of pics in one post. Unless that's changed I believe that's what it is.
Hope this helps
RC
