Screen Grab is a nifty add-on that allows you to take screen shots of a web page.
You can get screen Grab here:
https://addons.mozilla.org/en-US/firefox/addon/1146

Step #1
If there is a logo on a web page that you cannot copy and paste in to you image software then click on screen grab.
Screen grab is found on your status bar in the lower right hand corner.

Step #2
Then click on copy and finally select.

Step #3
Your screen will turn a shade of red.

Step #4
Use your cursor to highlight the area that you want to copy and then release your cursor.
You can now paste the logo into your image software.

Cheers
ingalls