Im not a technical writer so bear with me.

File formats: there are tons of different file types out there, but the best ones to use for web graphics are jpeg, gif and png. each of these has advantages and disavantages.

for smallest file size .GIF cant be beat, it also is a format that supports animation and transparency, the downside is image quality isnt as nice as a jpg or a png.

.PNG has exceptional image quality and also supports transparency without the crusty white outlines you get with a GIF, the downside is a slightly larger image file.

.JPEG is a happy compromise between image quality and file size, however it does not support transparnacy or animation. if you are posting a photograph .jpeg is your format of choice.

a couple things to know about file size and resolution, everything for the web displays at 72dpi if you make an image larger then 800 pixals across it prolly wont display in one screen on some monitors so your best keeping images under 700 pixels wide.

This gif is 300 pixals x 300 pixal at 128 colors and its size is 100k

this GIF is 300 px x 300 px but is 64 colors and the file size is 76k

This gif is 300px x 300 px at 32 colors its file size is 50k

you can see the slight difference in image quality but that is balanced by difference in file size. also you see what size 300 pixels are on screen, most web graphics dont need to be super big, 300 to 400 pixals for a photo is fine.

in photoshop use the save for web feature, this opens a palette that lets you choose numbers of colors and edit the image size, it also lets you select the format you save into like jpg, gif or png. using this will help reduce your file size.

if you dont have photoshop, there are some free applications for editing images, one that is really nice is GIMP you can download it here GIMP - Windows installers

there is a instruction manual that comes with it, there are also animation plug ins available for it for free.

Animated GIFs, animated gifs dont need to have a ton of frames, in photoshop or image ready you can even delete in-between frames and increase the frame delay, the animation wont be as smooth but then we are talking about a animated gif not a avi or mpeg file, most animated gifs can be effective with under 10 frames. it is critical that you use the minimum possible number of colors when saving your animation, this will do alot to reduce unnecessary file size.