Right click on the SC tray icon and select the item "Grab Windows Object or scrolling window" or hit default hotkey of Ctrl+Shift+PrtScr and then select the area to capture and follow instructions.
The scrolling capture works but it is pretty complicated and not automated. In the Hypersnap program it is a simple Ctrl+Shift+S command with the cursor positioned in the window. It is limited to vertical scroll. If you want to terminate the capture, just use the Esc key.
Pros and cons.
From what I've read, if you want to do captures in browser, you're better off using a browser add-on (than any screen capture app), or, in FF at least, there's an inbuilt way of doing it (there is a thread here somewhere ... see this
dc post, and following posts).