The reason why you're being redirected from some non-existing domain address to Level3 Search engine pages can be related to your DNS configuration or your ISP provider settings.
For example when using free DNS servers such as 220.127.116.11 (up to 18.104.22.168), normally they're used to locate the nearest DNS resolvers (especially useful for slow networks). See: What is 22.214.171.124? However please note these IP addresses are owned by Level 3's network, so they are basically redirecting you to their own search engine in case the domain is not found, because you're using theirs DNS. If you don't want to be redirected, simply don't use their DNS.
To check which DNS are you using, you can check in
/etc/resolv.conf or in Network Preferences of your connection.
Here are simple *nix shell command lines to check:
$ dig non-existing.domain
;; ANSWER SECTION:
non-existing.domain. 10 IN A 126.96.36.199
non-existing.domain. 10 IN A 188.8.131.52
$ wget -qO- http://184.108.40.206
<html><head><meta http-equiv="refresh" content="0;url=http://searchguide.level3.com/search/?q=http://220.127.116.11/&t=0"/></head><body><script>window.location="http://searchguide.level3.com/search/?q="+escape(window.location)+"&r="+escape(document.referrer)+"&t=0";</script></body></html>
So the redirect happens on DNS level by resolving any non-existing domain to Level3 pages.
To find out which DNS is redirecting you to Level3 pages, run this *nix command:
$ dig non-existing.domain | grep SERVER
;; SERVER: 18.104.22.168#53(22.214.171.124)
If you don't want the redirect to happen, change your free DNS to the one which ISP is providing for your network, or to your local DNS such as gateway/router IP.
Alternatively use different public DNS servers (which doesn't belong to Level3) such as:
- Google Public DNS: