Weird Safari (v8.0.2) Search Issue

Open the Safari preferences window and select the Search tab. Check the box marked

Enable Quick Website Search

if it's not already checked, then click

Manage Websites...

Remove any sites you're not interested in from the list. Spotlight may continue to index the remaining sites, even if you disable the search feature. To prevent that, remove all sites from the list.

If you don't want to use the quick search feature, uncheck the box.

My guess would be that you were using a search phrase starting with "the", like "the three musketeers", say. The search takes the first word as a possible hint about the site you want to search, so because "theregister" starts with "the...", anything you search for starting with "the" will trigger it. Took me quite a while to work out what was going on!