function sort(el) {
var col_sort = el.innerHTML;
var tr = el.parentNode;
var table = tr.parentNode;
var td, arrow, col_sort_num;

for (var i=0; (td = tr.getElementsByTagName("td").item(i)); i++) {
if (td.innerHTML == col_sort) {
col_sort_num = i;
if (td.prevsort == "y"){
arrow = td.firstChild;
el.up = Number(!el.up);
}else{
td.prevsort = "y";
arrow = td.insertBefore(document.createElement("span"),td.firstChild);
el.up = 0;
}
arrow.innerHTML = el.up?"↑ ":"↓ ";
}else{
if (td.prevsort == "y"){
td.prevsort = "n";
if (td.firstChild) td.removeChild(td.firstChild);
}
}
}

var a = new Array();

for(i=1; i < table.rows.length; i++) {
a[i-1] = new Array();
a[i-1][0]=table.rows[i].getElementsByTagName("td").item(col_sort_num).innerHTML;
a[i-1][1]=table.rows[i];
}

a.sort();
if(el.up) a.reverse();

for(i=0; i < a.length; i++)
table.appendChild(a[i][1]);
}