First use...
Eager beaver to use DeskCam with Firefox? Find here how to install it!
If clicking the "Install" button you can't install the extension you should go to next step, otherwisego straight to step 4.
Download .xpi extension file from this site (right click)
Installing the file. Two possible ways:
Always works - Start Firefox, open menu Tools > Add-ons and drag the file .xpi into the Add-ons window
Open the .xpi file with Firefox (i.e. on Win, right button on file icon and choose "Open with..." from the menu)
Reboot Firefox.
Now the extension is installed but webcam file has to be created and filled (that's the reason why on some sistems should appear an error message like "...preferences does not exist!"...don't care about it!).
In the end in Firefox open menu Tools > Add-ons > deskcam 3.x - Options/Preferences. The "Choose Webcams" window will opens.
Insert your favourite webcam URLs in the text fields well-formed according to the following sintax http://www.site-name.com/path/webcamname.jpg (i.e. "http://www.anziometeo.it/webcam/image.jpg").
At this point you just have to use DeskCam...Simply click with left or right button on the icon you should see appear in the bottom right corner of Firefox windows.