Firefox Browser Blinking Cursor Problem – Caret Browsing

Today something strange happens. While I start to browse the web with Firefox, the cursor is start blinking, the webpage start to feel like a word document. When I start using the down arrow, the cursor move line by line instead of the normal page scroll. It is so annoying after a while, because the page will not scroll right. This change of Firefox violate usage consistent. I google on this matter, I found this post
Turn off Caret Browsing by pressing F7 key. Try it yourself, what other feature you think your browser should be more friendly?