Safari will spontaneously visit URL while I type On my old MacBook Air and even on my brand new Retina MacBook Pro (which was set up as a new computer), if I open a new tab and quickly start typing a URL or search in the bar, Safari will sometimes truncate whatever it is I was typing and act as if I had pressed Return. 

I believe this has something to do with the search suggestions/seek time for bookmarks but it happens stochastically so I can't determine the root cause.
This happens if you:


have enabled Google as your default search engine
have enabled Google Instant within your Google search settings


I have this same situation occur on my Chrome.