document.onkeydown = function(e) {
	// Si el foco esta en un elemento de formulario NO ejecutamos las acciones de onkeydown
	var focus = null;
	// IE
	try{
		focus = event.srcElement.type;
	}
	// Mozilla
	catch(err){
		focus = e.target.type;
	}
	var form_elements = new Array('text','password','select-one','textarea','button','submit');
	var activar_keydown = true;
	for(var i in form_elements){
		if(form_elements[i] == focus){
			activar_keydown = false;
			break;
		}
	}
	if(activar_keydown){
		var url_prev;
		var url_next;

		if ( lnkprev = document.getElementById('crlPrev') ) 
			url_prev = lnkprev.href;

		if ( lnknext = document.getElementById('crlNext') ) 
			url_next = lnknext.href;

		e = (typeof e == 'undefined') ? event : e;
		keyPressed = (typeof e.which == 'number') ? e.which : e.keyCode;
		switch(keyPressed){
			case 37: // <--
				if(url_prev != undefined){
					document.location.href = url_prev;
				}
			break;
			case 39: // -->
				if(url_next != undefined){
					document.location.href = url_next;
				}
			break;
		}
	}
}