I have struggled with this for several days until I read the above posts. Clearing the history and cookies via the Settings/Safari window didn't work. Clicking on Bookmarks/History/clear didn't work. The problem is that you have a bookmark that has a URL that is showing up when you start typing in a fresh url.
When you save a bookmark, you can give it a custom title that is different than the url. What gets confusing is when you click in the URL field and start typing www, you get all these 'suggestions' that are actually the URLs of the bookmarks you've saved. If you have one 'offending' suggestion that you don't want to see any more, you will need to go through your bookmarks and check their URLs one by one.
To do so, click on the bookmark icon, click the 'edit' button in the upper right, then click on the bookmark - it will then show you the URL associated. (Note, don't click the 'edit' button until your inside your bookmark folders, or else you're just editing the name of the folder)