I'm a programmer (not a designer) and I work with various designers in the marketing industry. A typical project will consist of a designer coming up with a design for a web page and then handing the design off to me (PSD file or whatever) and I implement the design into a webpage (HTML, CSS, etc...).
The problem I run into a lot though is that a lot of designers don't know how to design with the web in mind. They come from a background of designing for print material, and they approach web design the same, which simply does not work. They don't think about things like "What happens to the design when the user changes the browser size" or "tileable background images" or designing using a grid/column system instead of placing elements all over the place or "You can't have a DIV with multiple background images that works for all browsers", or "don't use 12 different web fonts", etc...
How do I instruct designers on how to better design with the web in mind? Are there resource for this or books out there that approach the various challenges and hurdles to this? Or do they simply have to learn from experience?