I am unsure how to word this question so editing is greatly appreciated - edit before you downvote! How can I do something like Google has done:
https://www.google.co.uk/webhp?tab=ww&ei=d7hPU4L4IMOl0wWqzICICA&ved=0CBYQ1S4#q=stackoverflow
They have a question mark ('?') and then a variable which is set by the previous page. How does this work and what do I need to do to utilize it in my page, and with javascript? Please edit this if you know how to word it better.