Topic: pictures stretch on pc firefox, but format correctly on mac

I set up the viewer on a mac using dreamweaver, and it works great, but when viewed on a pc the image is stretched to fill the 480x480 window, and cutting off parts. i set the images up to have a max width or height of 480. I am viewing the website on firefox on both the mac and PC. maybe there is a setting I need to adjust so it is viewed correctly on a PC?

www amberstolec com

thanks