Right now if I type "test.jpg" into the URL bar, the response I get back is: "We can’t connect to the server at www.test.jpg" This seems like it leaks some information to your DNS provider unintentionally, which is undesirable. There might be a few ways to fix this; I propose that we add a better understanding of what a legitimate TLD looks like per: http://data.iana.org/TLD/tlds-alpha-by-domain.txt ... and only attempt to do a DNS Lookup on something ending with a recognized suffix. By default, we should do a search on the rest. This is related to bug 1411048.

I think decision about this is not made in necko/gecko. Moving it to firefox.

The second entry is always a search when we think something looks like a url. This is currently mostly a workaround because the Address Bar has no idea if the typed string may be a real domain or not. First of all because of bug 1080682, that depends on having a list of valid suffixes that is updated out-of-band, second because local domains can really be anything, I could have a "test.jpg" local domain, and we don't have the time to ask the dns. Btw, duping.