function changeTab(n,x){
    for(i=1;i<=x;i++){
	    document.getElementById("tab_"+i).style.display=(i==n)?"block":"none";
	    document.getElementById("tab_head_"+i).className=(i==n)?"isactive":"none";
    }
}
var timeout; 
function delayChangeTab(m,n,x){
    timeout = setTimeout("changeTab("+m+","+x+")",n);
}

function cancelChangeTab(){
    clearTimeout(timeout);
}