I have wanted to hide the statusline for a long time, but never got any luck to do by myself and to find a solution. It's hard to google it because people use wrong term. Some said "status bar," some said "command line." But the correct name is statusline, however more proper thing we are looking at is the grandparent node of statusline, bottombar. command line is only visible when you enter command line mode, so that's really not the right name.

Anyway, I read the FAQ and found there is already an entry about auto-hiding. The linked file is gone, but I did google and get the file. I didn't try it because that plugin has too many functions that I don't need and it's too old, I doubt it would work with latest Vimperator. However, it did give me an idea what element ID I should be looking for at first.

Now I have the following code in my rc:

map <silent> <C-F8> :js toggle_bottombar()<CR>

:js << EOF
function toggle_bottombar() {
    var bb = document.getElementById('liberator-bottombar');
    if (!bb)
    bb.style.height = (bb.style.height == '') ? '0px' : '';
    bb.style.overflow = (bb.style.height == '') ? '' : 'hidden';

Using Ctrl+F8 to toggle. Note that when you want to enter a command, you need to bring bottombar back first manually. I am sure I can hook/wrap something so when enter command line, the bottombar can be brought back automatically, but I am too lazy to find out how to do that.