function getElementsByClassName(classname) {
    if (document.getElementsByTagName) {
         var els = document.getElementsByTagName("*");
         var c = new RegExp('/b^|' + classname + '|$/b');
         final = new Array();
         var n=0;
         for (var i=0; i < els.length; i++) {
              if (els[i].className) {
                   if(c.test(els[i].className)) {
                   final[n] = els[i];
                   n++;
                   }
              }
         }
         return final;
    } else{return false;}
}

function muestra(classname)
{
	 var el = getElementsByClassName(classname);
	if(navigator.appName.indexOf("Microsoft") > -1){
		   var visible = 'block'
	} else {
		   var visible = 'table-row';
	}
	 for (var i=0; i < el.length; i++) {
		  el[i].style.display = visible;
	 }
	 
	 if(classname == 'extras')
	 {
	 	var btn = getElementsByClassName('extras_btn');
	 	btn[0].style.display='none';
	 }
}