why pdf

[violet]

hello
when i start up the myundergroundplace homepage, my explorer opens my pdf programm (not a file, just the programm).
this happens everytime when i hit a link, for example no watch other profils or the manage my account.
the forum goes normal, without open the acrobat.
what can i do that my computer does not open the programm everytime when i put a link?

thanks for helping!