How Can I Clear the Website Loaded on Startup?
As far as I know, there is not currently a way to tell an app to never remember its state.

You can, however, control this on an individual quit basis. That should be enough for you to get Safari to forget http://w/. Here's how:

Go to the Safari menu. Hold down the option key. You'll see Quit Safari change to Quit and Discard Windows. Click this item.

Now, reopen Safari. It should go straight to your homepage instead of to the page that was open when you quit.

If that doesn't work, it is possible that you've somehow set http://w/ to be your homepage. To change this, go to Safari-> Preferences-> General.