function validaletras(evt){	
var nav4 = window.Event ? true : false;
// NOTE: Backspace = 8, Enter = 13, '0' = 48, '9' = 57	
var key = nav4 ? evt.which : evt.keyCode;
return (key == 8 || key==32 || (key >= 97 && key <= 122)|| (key>=65 && key <=90) || key==193 || key==201 || key==205 || key==211 || key==208 || key == 225 || key == 237 || key ==243 || key == 250 || key == 233  || key ==241 || key ==209);
}