var counter=0;
var op_a=0;
var op_b=0;
var op_c=0;
var op_d=0;
var op_e=0;
var op_f=0;

function fader_double(){
	var itema=document.getElementById('content_a');
	var itemb=document.getElementById('content_b');
	var itemc=document.getElementById('content_c');
	
	var itemd=document.getElementById('content_d');
	var iteme=document.getElementById('content_e');
	var itemf=document.getElementById('content_f');
		
	itema.style.display='block';
	itemb.style.display='block';
	itemc.style.display='block';
	itemd.style.display='block';
	iteme.style.display='block';
	itemf.style.display='block';
	
	counter++;
	if(counter>1000){
		counter=0;
	}
	if(op_a<0){
		op_a=0;
		op_d=0;
	}
	if(op_b<0){
		op_b=0;
		op_e=0;
	}
	if(op_c<0){
		op_c=0;
		op_f=0;
	}
	
			
	if(counter>0 && counter<100){op_a++;op_d++;}
	if(counter>300){op_a--;op_d--;}
	
	if(counter>300 && counter<400){op_b++;op_e++;}
	if(counter>600){op_b--;op_e--;}
	
	if(counter>600 && counter<700){op_c++;op_f++;}
	if(counter>900){op_c--;op_f--;}
		
	
	itema.style.opacity=(op_a/100);//for firefox
	itema.style.filter = "alpha(opacity:"+op_a+")";//for ie
	
	itemb.style.opacity=(op_b/100);//for firefox
	itemb.style.filter = "alpha(opacity:"+op_b+")";//for ie
	
	itemc.style.opacity=(op_c/100);//for firefox
	itemc.style.filter = "alpha(opacity:"+op_c+")";//for ie
	
	itemd.style.opacity=(op_d/100);//for firefox
	itemd.style.filter = "alpha(opacity:"+op_d+")";//for ie
	
	iteme.style.opacity=(op_e/100);//for firefox
	iteme.style.filter = "alpha(opacity:"+op_e+")";//for ie
	
	itemf.style.opacity=(op_f/100);//for firefox
	itemf.style.filter = "alpha(opacity:"+op_f+")";//for ie
	
	setTimeout('fader_double()',20);
}