.png

Pros: transparent background, excellent quality, good w/ color

Cons: too big

.pdf

Pros: universal, any OS Cons: never meant to be web image

.tiff

Pros: excellent quality

Cons: no longer used on web, gigantic size and slow

.svg

Pros: quality

Cons: takes a lot of code

.gif

Pros: animated

Cons: not good with photos

bitmap

Pros: small file

Cons: no color, poor quality, dated