Have a talk with your network administrators, OP. It is their poorly configured filtering and monitoring appliance that is causing you errors.
https://encrypted.google.com/search?q="ALLOW_ADMIN_ERROR_PAGE"
https://duckduckgo.com/?q=HTTP+504

Cisco apparently ain't gots noez loves for DDG. D:

"Decision_Tag=BLOCK_UNSUPPORTED_SEARCH_APP_11-DefaultGroup-DefaultGroup-NONE-NONE-NONE-NONE&URL_Cat=Search Engines and Portals"

Try using the HTTPS enabled version of DDG and see if that works. Sometimes stupid machines or lazy admins either don't filter SSL or have no capabilities to MiTM the key exchange. I have no experience with this particular device but it may also have controls over or tie in with your company DNS system. Try a DDG IP address.
184.72.115.86  or  184.72.106.52 If you don't trust me to give you the proper IP, look them up yourself.

 Alternatively, if you're even able, you can SSH or VPN to a remote system (beyond your corporate firewall) that you personally control to get unfettered net access. I recommend SSH (if able) because VPN takes your connection hostage and you won't be able to reach the company Intranet like that.


Also: Use a space or your Enter key between the URLs next time. That thing looks god awful.

--
Pierce