Down at the bottom of the screen, where the icons are, click there and “tile” the open icons. That will “hold” the mail and other folders open so you can “drag and drop”.
I don’t think it is that, unless I am misunderstanding you. The various windows tile themselves automatically, don’t they...?
Forgot to mention, this is Firefox and I am thinking it’s an issue with the browser. I see on the Firefox forum there are some undealt-with gripes about Firefox “stealing focus”. That could be (the name of) the issue. There appears to be no cavalry riding in with the big fix.
Think I found the solution:
http://www.techsupportalert.com/content/how-stop-firefox-stealing-window-focus.htm
How To Stop Firefox From Stealing Window Focus
Updated 19. September 2011 - 6:32 by rhiannon
Prevent Firefox from opening when you’re doing other things
Firefox turned 5 this week. While no other browser to date has been able to lure me away from Firefox since its first early beta, it does have its flaws and frustrations.
One of the most annoying habits Firefox has is stealing the focus from other programs you are working in. Clicking on a hyperlink inside programs such as email or office type applications causes the link you clicked on to automatically open inside Firefox. For example, I’m reading email, and I click on a link inside the email. All of a sudden I’m looking at a Firefox window showing the web page that the email link goes to.