function hidetabs() {
    for (var i=0;i<blocks.length;i++) {
        document.getElementById("tab_content_"+blocks[i]).style.display = "none";
    	var el = document.getElementById("tab_"+blocks[i]);
	    el.src = el.src.replace("_active","");
	}
}

function show_tab(id) {
    hidetabs();
    document.getElementById("tab_content_"+id).style.display = "block";
    var el = document.getElementById("tab_"+id);
    el.src = el.src.replace(".jpg","_active.jpg");
}