function file(fichier) {
	if(window.XMLHttpRequest) // FIREFOX
		xhr_object = new XMLHttpRequest(); 
	else if(window.ActiveXObject) // IE
		xhr_object = new ActiveXObject("Microsoft.XMLHTTP"); 
	else 
          return(false); 
	xhr_object.open("GET", fichier, false); 
	xhr_object.send(null); 
	if(xhr_object.readyState == 4) return(xhr_object.responseText);
		else return(false);
}

function screenOpac() {	
	var bodyElement = $(document.body);
	var myDiv = new Element('div', {    
	    'id': 'div_opac',
		'styles': {
			'position':'absolute', 
			'top':'0', 
			'left':'0', 
			'width':'100%',
			'height':this.getScrollSize().y, 
			'filter':'alpha(opacity=40)', 
			'-moz-opacity':'0.40', 
			'opacity':'0.40', 
			'background-color':'#000000', 
			'z-index':'400',
	        'display': 'block'
    	}		
	});	
	myDiv.inject($('div_body'));	
}