Today's websites rely heavily on imagery to get the message across - whether that be branding, context descriptions or just simple photo galleries. However, large images can not only slow your site down, they take up space on your host server, often bumping your hosting account up to the next cost level. 

I use the services of a graphic designer to help with a lot of my client work, to make sure images are set exactly for the web but this is an extra cost that some clients don't want to have to bear.  Here's a great article I have found on how to make images for the web, right from the first point of even taking the photos yourself! 

How to get images right for the web