function tab_load(tab_name) {
    if (!tab_name) tab_name='home';
    show_content(tab_name);
}
var visible_tab_id;
function show_content(div_id) {
    var div=document.getElementById(div_id);
    if (!div) return;
    if (visible_tab_id) {
        var old_div=document.getElementById(visible_tab_id);
	if (old_div) {
	    old_div.style.display='none';
	}
    }
    div.style.display='block';
    visible_tab_id=div_id;
}