Why is my url way longer than it should be in the box?

If i search "yahoo questions" in google in the url box thing it says "http://www.google.com/search?sourceid=c… but if i stay on the same tab/window and search, say, "unicorns" and then "autotrader" it'll say "http://www.google.com/search?sourceid=c… which is a lot longer than seemingly necessary...could i have downloaded a cookie or something? and i dont think that it shows the full link but its really really long with random numbers and letters