Calling none-static server method from javascript?

Question

Is it possible to call server side methods? (with postback)

This will post back as if I clicked the button1.

 var prm = Sys.WebForms.PageRequestManager.getInstance();
prm._doPostBack('Button1', '');

The problem with that, is that I need a button on the page.

I know I can use static webmethod, but I want to know if it's possible to call a regultr method.