Whenever I type a search term into Firefox's address bar that contains a period, my ISP is displaying a custom "not found" error page because a look up for explorer.exe will fail for obvious reason.
I dislike the highjacking of my searches and use the "?" workaround usually to run searches for all types of queries automatically. If you search for ?explorer.exe, Firefox will automatically run a search for the term.
It depends on the DNS provider if a custom error page is shown or not. There does not seem to be a setting in Firefox to block this behavior, and the only option that you have is to switch provider or use the "?" workaround instead.
If you are a free user of OpenDNS you may have experienced a similar situation. Whenever you try to access a domain name that does not exist, you are redirected to a custom error page with advertisement on it.
The search and results appear to be powered by Yahoo, and the domain you are redirected to is website-unavailable.com.
The only way around this up until now was to switch to a paid package instead.
OpenDNS announced today that it will retire OpenDNS Guide on June 6, 2014 for all free users of the service. What this means is that free users won't be redirected to a custom search page anymore when they type a domain name into the browser's address bar that cannot be resolved automatically by DNS because it does not exist.
Instead of seeing the custom search page, free OpenDNS users will see the solution that the browser maker has baked into the product. This can be a custom search page or a simple error message that the server could not be found.
The change does not affect any other features of the OpenDNS service.
Why is OpenDNS making the change?
According to David Ulevitch, founder and CEO of OpenDNS, there are several reasons for that. When the company started out, it decided to use ads to finance the service.
This worked out well in the beginning as browsers did not interfere with those look ups in any way. The rise of Google Chrome has changed that, and as a result, the revenue source has declined over time.
OpenDNS started to concentrate on its paid products for revenue generation and the consequence of all this was the decision to retire the guide and the ads page.
Free OpenDNS users will benefit from the decision as searches and look ups won't be highjacked anymore by the company's DNS system.