I suppose that one of the reasons I've had little trouble with JPG is that I usually work in Photoshop native .psd and size before converting to the .jpg. JPG can get pretty ratty if you change size after converting, and for lineart it can pixilate easily.

The belief that .gif is a "lossless" compression method is something of a myth. The compression is lossless, but the coversion to indexed color throws away a whole lot of picture information before the compression is done. Re-saving doesn't lose any additional info, but the first conversion to .gif dumps a lot of any image that starts out with "chromatic" color. GIF also uses LZW compression, which is a "patented" process so royalties must be paid - usually by the programmer who provides the ability to make them in a graphics program.

PNG is a "much improved gif," but unfortunately many older browsers don't handle it well.

Probably the most "universal" format is TIF (or TIFF for purists) but since it's an "extensible format" and programmers can modify the file layout to suit their own "special needs" there are so many flavors of TIF around that problems come up fairly frequently when moving from one program to another.

JPEG isn't actually a "format." It's really just a compression method, that can be applied to several formats. All .jpg files you're likely to run into actually are .tif of one kind or another compressed using the .jpg compression method. Purists will want to look up the JFIF spec (Joint File Interchange Format), which actually does define a format commonly appearing with JPEG compression.

A quick summary of graphic file types usable in Windows Office programs can be found in Guidelines for selecting the appropriate picture format, Mickey's KB article 272399. It's not exactly the last word on the subject, but may be a useful summary.

John