function myDisp(myID,myDisplay){ 
myObj = document.getElementById(myID).style; 
myObj.display = myDisplay; 
} 

var countID = 0;

function count() {
countID++;
myID = "s_"+countID;
prevID = "s_"+(countID-1);
pageID = "p_"+countID;
formID = "f_"+countID;
myDisp(myID,"block"); 
myDisp(prevID,"none");
myDisp(pageID,"none");
myDisp(formID,"block");
}