getting an odd message when searching in browser's address bar

Question

So I searched adblock in the firefox address bar and it redirected to a page "http://domainnotfound.optimum.net/cablevassist/dnsassist/main/?domain=adblock" that said:

Server Error in '/' Application.
Runtime Error
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.

Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customErrors> tag should then have its "mode" attribute set to "Off".


<!-- Web.Config Configuration File -->

<configuration>
    <system.web>
        <customErrors mode="Off"/>
    </system.web>
</configuration>


Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's <customErrors> configuration tag to point to a custom error page URL.

I'm just trying to use ubuntu for basic browsing. Nothing that would cause a message that says there's some server error and custom server settings (which a browser on the network should be able to see but I can't even though my browser is on my home network.

Answer 1

Typing some words in the Firefox address bar will result in Firefox doing a web search for those words. Typing other words will result in Firefox treating the word as a hostname and trying to connect to it.

I do not know how Firefox decides which words to use as search terms, and which to use as destination addresses (if you do know, please let us know).

• "hello" - treated as search term
• "hellox" - treated as address
• "ping" - treated as search term
• "pinga" - treated as address
• "askubuntu" - treated as address
• "user278904" - treated as address

What happens when Firefox treats a word as an address, and it can not be resolved, depends on your ISP. Traditionally, an unresolved address would result in a DNS lookup returning an "unresolved" status, and Firefox then complaining that it could not find the server. Unfortunately, some ISPs realised that they could instead resolve unknown addresses to point to their own internal servers, and then serve their customers targeted advertising based on the site that they tried to connect to. This appears to be what is happening in your case. Your ISP is intercepting your unresolved address, and redirecting it to one of its own servers. The server in question was temporarily configured incorrectly, resulting in the odd error you saw - this now seems to have been fixed and visiting the URL you gave results in optimum.net serving up "adblock" related adverts.