Google page rank! Need help!

i have a problem with my google page rank,
i have tried one specific keyword and

(mysite),com - ranks 300
www,(mysite),com - ranks 113
www,(mysite),com/ - ranks 80

why is that happening & what should i do?
(i read that for google (mysite),com & www,(mysite),com are two different urls, + when i add "/" i rank again my site differently...)

Yes google think it is two different urls so you should get different results in search engines. You should concentrate of building backlinks and www too only.

Second this is not called page rank this is called keyword rank position. Page rank is a different thing PR1234-10.

yes my bad! but why there is a difference between www,mysite,com & www,mysite,com/ ?