gistfile1.js

var eles = document.getElementsByClassName("detail");
function doNext(curIndex){
	var ab= eles[curIndex].getElementsByTagName('a');
	if(ab[0].innerHTML.indexOf("Free") > -1) ab[0].click();

	setTimeout(function(){
		if(curIndex < (eles.length - 1)) {
			doNext(curIndex + 1);
		}
	}, 500);
}

doNext(0);