by jimbobo2779 » Wed Jul 16, 2014 7:03 pm
You can make sure that you have NHP set to check your proxies between 12 -15 minutes, output every 1 minute and that NHSEO is set to load in the proxies every 60s (60000).
Doing the above will mean you are using the freshest list of proxies available to you and will limit these fails as much as possible.
Other than that you will always see these messages, sometimes you won't see any and other times you will get a log page full of them, it is just random as you (or NHSEO) cannot control the targets that the search engines return for posting to so until NHSEO visits the address it does not know whether the page is up, whether it is using a supported platform and whether the platform is setup to accept links or not.
As you suggested it is just a part of link building.