// shared js functions
function setTab(id)
{
	// select / unselect tabs and content blocks
    for (var i=1; i<=4; i++)
    {
        var tab = document.getElementById("tab" + i);
        var div = document.getElementById("doc-content-" + i);
               
       if (i == id) {
			tab.className = "selected";
            div.className = "visible";             
	    }
       else {       
            tab.className = "";	
			div.className = "invisible"; 
	    }
    } 
}