How can I remove an autocomplete suggestion from Safari's address bar?
Open Safari.
From the “History” menu, choose “Show All History”.  


keyboard shortcut: ⌘ Y

In the Search field in the top right corner, enter the web site you want to remove.
In the list of search results, click on the web site you want to remove.  


To select multiple sites, hold the command ⌘ key while clicking on the sites you want to delete.  Or, to select a range, hold the shift key, click the first item to delete, then click the last item to delete.

Press the Delete key on your keyboard.