You'll get a lot of stuff off A sites. There will be over 50 photos to see as well as new material a lot of the time. Bookmark A sites update because they get lots of activity, or are very popular. A sites rarely go down for anything.

B sites are pretty good. They have good information and/or some good photos. Updates may be be maybe once a month or so, but are still good nonetheless. B sites may go down for a slight time due to bad servers or bandwidth.

C sites are for websites that rarely update (once per 2-3 years), have bad links, or have very little railroad information on them, like one page websites for instance. C sites could be better, but still worth a look.

D sites are back! These websites or manufacturers are very bad. Look if you dare!