How to reduce the size of an jpeg format image???

You have two way to make this: 1. Open the image and resize it to a lower dimension. 2. Open the image and save it with a lower quality. If you want to use the first way I should have a good image manipulator software like Photoshop, Corel Draw or Paint Shop Pro, if you want to use the second way it is sufficient a cheaper software. If you use Linux you can use both ways with Gimp.