How can I change Alt+click to Shift+click?

Hi!

I am using Iceweasel on Debian Linux Lenny, because SeaMonkey does not
properly work.
If I want to download a file, then I am used to press the Shift key
and click with the left mouse button
at the link. Then, a "save as" dialog appears.

At Firefox/Iceweasel, I have to press the Alt key instead of the Shift
key. The problem is that
my window manager uses the Alt key in combination with the left mouse
button to move a window,
and I do not want to abandon this useful feature.

So, it is not possible to use Alt+click in my environment.

Is there a way to configure Firefox/Iceweasel to make Shift+click open
a "save as" dialog?

dolphin