It is necessary to compress photos before they are uploaded to a website so that pictures appear instantly on screen and viewers don't have to wait for pictures to download. It also makes them easier to email.
Go to the tools area of the Microsoft website from where you can download a 'Powertoy' program which will enable you to compress images just by right-clicking over them. (Choosing 'select all' and right-clicking enables you to compress many photos at the same time.) Other more sophisticated programs can be used to edit images but this is the simplest way that I have found.
A typical photo taken by a digital camera will be over 1000kb (= 1mb) in size. For web use the photo needs to be compressed < 100kb. Photos taken by mobile phones are usually much smaller and easier to send.
For more information about compressing images etc go to this page at Cumbria & Lancashire Education Online.