For those that read this article... under "Using Valid code" they explain to apply a custom "class" however they use an ID tag (#).
#fullheight{height:100%}
As far I know, the id tag can be used only oncein the document. The proper way would be to change the "#" to an "." . This would, in effect, change from an Id to a class and then can be used more than once within the document.