[R] t-test between percentages

[Bunny, lautloscrew.com]

Hi all,

though i know this is a simple question, i really hope someone could.
I am just trying to compare percents respectively the difference in  
percents by a simple test. t.test usually compares means and is  
working like it is supposed to be. Now i wonder how i can use a test  
in R to test for significant difference between two percentages.
http://survey.scantron.com/resources/significant-calc.htm is pretty  
much all i need.

How can i solve this in R ?

thx in advance

m.