I want my browser to tell me it can't find a url that doesn't exist. It's faster that way.

Comcast has now enabled something they call "Domain Helper Service" which redirects bad url's to a comcast search engine.

I've opted out, but it seems somewhat persistent.

Time Warner did this a while ago as well in my area, and did something to their DNS servers to break Back to my Mac. My fix was to switch over to OpenDNS, and also disable all their "helpful" pages.

The worst part for me is that the browser wouldn't know I typoed a domain, and remember it, causing it to suggest the typo version in the future as an autocomplete suggestion.

Yeah, OpenDNS solves that pretty handily, and gives you other benefits in the process.

After an online chat with comcast, the "domain helper service" is now turned off.

I needed to,
1) Change a comcast account setting
2) Restart the modem
3) And clear the dns caches of my computers.

2&3 Not being mentioned as necessary on the page where the service is disabled.

That's cool that they let you turn it off.

I was using open DNS but I didn't disable the auto search stuff. I almost always just type the name of the site into google. Then even if I spell it wrong it's almost always at the top of the results.

That isn't infallible. People have and do work out ways of messing around with the ranking of sites so their scam/ad site gets higher than the real site.

That is true but i'm not doing a "i'm feeling lucky" the real site is pretty close to the top and it's not too hard to tell which is the real one.