The following images give you an idea of the kind of quality you can expect from gif and jpeg images, what they're best used for, how the quality is effected, and the difference in file size.

1.vgood quality jpg image 63kb 2.average quality jpg image 21kb 3.crap quality jpg image 16kb
4.(256col) gif image 29kb 5.(100col) gif image 17kb 6.(50col) gif image 14kb
7.vgood quality jpg image 30kb 8.average quality jpg image 13kb 9.crap quality jpg image 11kb
10.(256col) gif image 31kb 11.(100col) gif image 18kb 12.(10col) gif image 9kb
13.vgood quality jpg image 50kb 14.average quality jpg image 21kb 15.crap quality jpg image 16kb
16.(256col) gif image 14kb 17.(100col) gifimage 12kb 18.(4col) gif image 4kb
   
18.(4col) gif image 4kb transparent