What is 'Curl Check'?

When I tried to submit a new sites' links to Digg I got this message every time I tried:
"Your link is invalid, please check if you didn't write it properly" though all my links were copy$paste, so I contacted Digg support to explain the issue, and that was their reply:

After that I tried to know more on what is "Curl Check" and how to fix this issue, but I didn't got anything.
So, my 2 questions is:
What is 'Curl Check'?
How to fix this issue?
Thanks

 

Think of curl like a web browser. It's basically a command line utility that sends a request to a web server like a web browser does. (web programmers can use it to scrape information they need as well) When you say it's a new site, how new are we talking? Like a day old? If so, the DNS may not have fully propagated and Digg's servers wouldn't be able to resolve the domain name to the IP.

If it's more than a week old, then there's something else going on that's preventing Digg's servers from being able to access your site properly.

 

it's like a ping for a websites availability

curl FULLURL

will return the index.

Does Digg care about robots.txt for this check?

 

The site is not new, Its some months old.

 

I don't know
I really hope someone knows!