function change_content(id_content){
	document.getElementById('concept').className = "ukryj";
//	document.getElementById('man_concept').style.border = "none";	
	document.getElementById('graphic').className = "ukryj";
//	document.getElementById('man_graphic').style.border = "none";		
	document.getElementById('realisation').className = "ukryj";
//	document.getElementById('man_realisation').style.border = "none";		
	document.getElementById('promotion').className = "ukryj";
//	document.getElementById('man_promotion').style.border = "none";			

	document.getElementById(id_content).className = "pokaz";
	var my = "man_" + id_content;
//	document.getElementById(my).style.border = "#FFFFFF solid 1px";
}