Always set input focus to the search textbox
Normally after you click a Google search result link and check out the page, upon then returning to the original search page you would have to manually CLICK in the search text box to update and refine your search terms.
This script automatically moves the input focus to the search text box whenever the page becomes active/focused, so you can immediately start typing to update your search text.
Just think of the milliseconds you'll save...