I have a good deal of users who need to print certain pages of an intranet application for record keeping. We used to have "printer friendly buttons" (I nixed them after asking this question) that butchered the user experience and navigation controls while on the actual web site.
In replacement I've added a CSS which automatically formats any page on the site for print reasonably well, but I'm concerned if users may get frustrated because they print something not exactly like they see on the screen.
A large part of the solution in my case has been printer buttons; I know which pages my users print (explicit reports are supposed to be printed for backups) and gave printer buttons to print out specific reports. The site is mostly navigation and tables of database data.
I like the buttons because I found many of my users don't actually know how to use standard print commands; however slapping the printer button on every page seems very unnecessary, and I can't exactly give a popup every time a user prints that says "This page will look different on paper." Is this an issue to be concerned about?