The difference that draws my attention is that print media is static - ink or other compound is bonded to a page and is permanently fixed. Unlike a web site, there is no hope of that print jumping up and rearranging itself if the user wants to see a different layout. The first difference is that web publishing has the possibility of introducing dynamic content to the user in a number of different ways. Web sites used for e-commerce have the ability to show customized content based on the user’s past purchase history, or if they have a particular preference for how the page is arranged. My Yahoo is another example, where each user can have a customized view of information they choose.
The other primary difference I can think of between web and print media is that designing for a newspaper, for example, is a controlled process from end to end, unlike a web page in which the rendering and quality of the final product is out of the control of the publisher of the content. The newspaper publisher chooses layout, fonts and other aspects of style just list a web published would, but the similarity stops there. A print publisher also chooses the rendering mechanism and the paper it is printed on. In web publishing, that last step is somewhat variable in that browser differences have the possibility of producing different output with the same HTML code.