I'm putting together a website that I want to fit to 1024 x 768 resolution but I want it to shrink to fit proportionately when at 800 x 600 resolution.

My website will use frames and percentages to solve certain parts of what I'm trying to do but I've a lot of images that will sync up with other images. I've breifly looked at the sniffer method of working but what I want to know before I start is:

Is there a way of using a sniffer to change the size of every jpeg and file to a percentage that fits the smaller resolution, I worked out that the 800 x 600 is 61% of 1024 x 768.

Thanks for any replies.