Whomever runs your company's network will have that site in their list already.
So most likely at this point it won't matter what "header" or "meta-data" changes 13skills.com will make,
it's already on the "naughty" list as far as your work's proxy / caching server goes.
If you can't talk to the sysadmins or network team to convince them to "white-list" this site,
you could try and go around the block with something called an online proxy, or anonymous proxy.
Just Google either of those terms.
Though a word of warning; if your company is big enough to setup a black-list proxy for their network,
they will most likely have an Internet Usage Policy, and using a anonymous proxy will most likely violate that policy.
I'd ask first, perhaps offer them cookies or pizza, sysadmins love food!
