Several browsers ignore some aspects of print css files in unexpected and undesirable ways. I have compared the online and local printing behaviour of Camino 1.6.3, Explorer 5.2.3, Firefox 3.0.1, iCab 4.2.0, and Safari 3.1.2. Unless noted all browsers behave the same online as locally.
My first test page has a single 768x1024 point image with dimensions defined in separate identical (except for background colour) screen and print css files. All test browsers display this correctly on the screen. Since the image is defined to be larger than the A4 it is to be printed on I would expect the default print behaviour to result in four pages with partial images. Only Explorer achieves this and has convenient controls to crop or print wide images. Camino and Firefox have a 'shrink to width' setting which Camino ignores. Without this setting selected they both correctly print the first page full size with a partial image but critically they both ignore the partial images on the other 3 pages. In online mode only Firefox 3 annoyingly prints a second page which is blank except for the background colour. iCab and Safari enforce 'shrink to fit' contrary to the print media css.
My second test is the same as the first except that the image is split into 12 off 256x256 point images constrained by a div slightly wider than 3 images. The results are the same as above except that Camino and Firefox now print the previously missing lower partial image on a second page but still fail to print the missing partial images from the right.
My third test page consists of the single image page in a frame. This has little effect on most browsers except that Firefox 3 no longer prints the annoying blank second page and iCab bizarrely only prints a small fraction of the image unless one clicks on the page (frame contents) prior to printing.
I have not printed every combination of pages - I have relied upon Preview to show what will be printed but I have no reason to believe that this method of testing is unsatisfactory. I am using OS X 10.5.5 on a G4. In general all browser settings are similar - 100%, no headers/footers, minimum borders etc - iCab margins are all set to 12pt (without this setting the combination of iCab and my LaserWriter 16/600 lose an indeterminate amount of data around the edges.
Demonstration pages can be found at: