How is download protection done on the site?

Question

PHP

Interested in the site php.su , using wget no answer from php.su wget -r -k -l 7 -p -E http://php.su
Here is the question , how did the developers make the protection ?
I downloaded a lot of sites through wget for offline viewing, even php.net and this site was the first one that was not downloaded ..

Answer 1

They check by User-Agent, maybe cookies.
How to download a site with wget with cookies and userAgent?