Sally,
You can use software to change the resolution of the images. In Windows XP the default photo software can do it.
It is normally an option from Images on the menu - resize them to around 640 by 480 pixels - this is usually a good size for the internet.
Also if you do no already save then as JPEG type - this is a compressed format.
The advantage of keeping the images small for the internet is the time it takes to view them on peoples computers.
To give you an example of image size / quality if you look here
http://www.danfulton.com/a4a/a4a/index.php?board=8;action=display;threadid=1508on the new board, those pictures are all 640 by 480, and less than 50K in size !
Hope that helps
Dan