When you using your iPhone mobile Safari you can save a copy of a image you see on a site your viewing.
When you tap and hold your finger on an image for a couple seconds, you will get an option to save the image or to cancel. If the image has a link assigned to it on the Web page, you will also have a button to choose to follow the link like you had clicked on it with your mouse on your desktop computer.
Choosing to save the image, the Web browser will return to the site. To access the image you just saved, launch the iPhone’s Photo area – there you will find it in with the images area of pictures you have taken with the build in camera.