Assuming you are using Winders (I don't know about MAC or LINUX, etc.) if you right click on something in a browser window you will get a "context menu" and in that menu is a selection "Properties" (usually the bottom entry). Click that entry and you will get a dialog box that should list the Address (URL). That will tell you what server company is hosting the image or text you clicked on.
Most of the time on the Trains forums you will see something that begins with:
"http : // cs . trains . com / blah blah blah"
Note: even if the URL is not of the company you expect it does NOT mean it is not a legitimate item, but it can sometimes help you determine if it IS legit. i.e.: Trains Magazine might be in a contract with some other company to store something for Trains, or maybe the other company is paying Trains to call something from their server, but if it is "Trains dot com", then it is from the Trains dot com server.