It's time for some bitching and whining.
Some time ago I had a meeting with potential client who has ordered site design from a well known local ad agency and wanted my company to program the eshop. He showed me printed mockups of the site which were quite nice visually.
Later, as we talked further, he emailed me the same mockups in jpeg. I've noticed that content part of the site (a static width design) was 1300+ pixels wide. I informed the client that this is way too wide for a site and asked to make the design fit into 960 pixels. A couple of weeks later I've received new mockups where all that was done was the whole design proportionally resized to fit into 960 pixels.
When I pointed out that in some elements font sizes became unacceptably small (one button had text on it with 4px high font!) I got a few emails from the ad agency's project manager and then a call from a higher executive who in quite arrogant way tried to convince me that I can't make these judgements from JPG mockups but I have to get their magnificent CorelDraw file and everything will be fine. To my note that 4 pixels is 4 pixels and it's not enough for the text to be readable no matter how crisp it is, he responded with typical print designer gibberish talking about centimeters, 72 DPI, 150 DPI and other crap that has totally no relevance in web/screen design. He also noted that client has signed out on the design when they demonstrated it to him in their office (most likely on a shiny Apple's 30" screen with 500% zoom). I understood that I have no chance to convince these people to admit that they know nothing about web (after all they are well known ad agency!) and listen to my free advice. So I decided just to make a mockup web site with the design and show it to the client so he sees it in "field" conditions. We'll see how it goes.
After the conversation I was curious to find the origin of the 72 DPI tale so I googled it and found a perfect article - "Say No to 72 dpi" - which should be mandatory to every print designer before he or she is allowed to do anything for the web or screen. I suggest you read it even if you have a good idea what pixel is. It's hilarious. And definitely bookmark it so you can send it if you ever have a conversation like mine. After all since the web is total mainstream these days more and more people start designing web sites and print designers are leading the pack since the already know everything about design. And definitely more than those arrogant programmers!
Bonus design tip: Did you know that you can change black-gray-white-greenish site template to black-gray-white-bluish by simply swapping B and G values in RGB colors? :) This is what I did to convert the theme of my personal blog to this one.