function doc_height() {
    var doc_height;
    if (self.innerHeight) {// all except Explorer
	  doc_height = self.innerHeight;
    }else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
	  doc_height = document.documentElement.clientHeight;
    }else if (document.body) {// other Explorers
	  doc_height = document.body.clientHeight;
    }  
	return(doc_height);
  }