Prot Warrior Armor question

[Thunderballs]

I've heard people talking about armor caps...

Can I get more info on this please? Is there a cap? If so what is it?

Armory link to my Warrior
http://www.wowarmory.com/character-sheet.xml?r=Blackrock&n=Thunderhorns

[Salubrious]

http://www.wowwiki.com/Armor

pretty much explains it, for level 83 attackers (current raid level bosses) the cap is 49, 905