last_tab = 'tab1';
function show(layerName) { 
document.getElementById(layerName).style.display = '';
} 

function hide(layerName) { 
document.getElementById(layerName).style.display = 'none';
} 

function show_next(tab_name) {
document.getElementById(last_tab).className = 'tab';
var curr = document.getElementById(tab_name);
curr.className='tab_hover';
hide(last_tab+'_data');
show(tab_name+'_data');
last_tab=tab_name;
}

function toggleLayer( whichLayer )
	    {
var elem, vis;
if( document.getElementById )
elem = document.getElementById( whichLayer );
else if( document.all )
elem = document.all[whichLayer];
else if( document.layers )
elem = document.layers[whichLayer];
vis = elem.style;
if(vis.display==''&&elem.offsetWidth!=undefined&&elem.offsetHeight!=undefined)
vis.display = (elem.offsetWidth!=0&&elem.offsetHeight!=0)?'block':'none';
vis.display = (vis.display==''||vis.display=='block')?'none':'block';
}