Firefox - Take screenshot of full page

Solution : 1
1. Update with latest Firefox.
2. In right side of the address bar, there is Page Actions menu (three dots)
3. Click on it and select option "Take a screenshot"
4. Either select option full page or visible page.
or
Right click on the page and select option 'Take a Screenshot'
Here you can take screenshot of full page or visible page.

Solution : 2
1. Press key Shift + F2, Firefox console will be visible
2. Run command
screenshot --fullpage
3. It will save screenshot of whole page in default download folder.

Solution : 3
Use addon screengrab