function showhidetabs(tab){
	var d=document;
	var first=d.getElementById('first');
	var second=d.getElementById('second');
	var third=d.getElementById('third');	
	var fourth=d.getElementById('fourth');
	
	var tabfirst=d.getElementById('tabfirst');
	var tabsecond=d.getElementById('tabsecond');
	var tabthird=d.getElementById('tabthird');
	var tabfourth=d.getElementById('tabfourth');
	
	tabfirst.className='';
	tabsecond.className='';
	tabthird.className='';
	tabfourth.className='';
	
	first.style.display='none';
	second.style.display='none';
	third.style.display='none';
	fourth.style.display='none';
	
	d.getElementById('tab'+tab).className='selected';
	d.getElementById(tab).style.display='block'}