Why can't I upload pics on certain sites [duplicate]

Mobile safari before iOS 6 does not have access to data from the camera roll or photo application by design.

iOS doesn't have a common space to store files like computer users have come to expect. Instead, each app is "sandboxed" and can only see the data it created/downloaded. Apple provides API for one program to request data from another. Mobile Safari would need to have hooks to allow a web site to ask to use the photo chooser for image upload to work. So the design makes it hard to upload files in the way most web sites expect on iOS.

The best you can do is use another app like the flickr app to push photos to the internet and then link back or upload from a URL. It's clumsy but works without you waiting for mobile safari to change or updating to iOS 6.