function mostrar_ocultar(elemento)
{
    if(elemento.style.display=='none') elemento.style.display='';
    else elemento.style.display='none';
}

function cambiar(elemento1,elemento2)
{
    if(elemento1.style.display==elemento2.style.display)
    {
       elemento1.style.display='';
       elemento2.style.display='none';
    }
    else
    {
        if(elemento1.style.display=='none') elemento1.style.display='';
        else elemento1.style.display='none';
    
        if(elemento2.style.display=='none') elemento2.style.display='';
        else elemento2.style.display='none';
    }
}
function acceptNum(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 <= 13 || (key >= 48 && key <= 57 ) || key==46);
    
}

function seleccionar_checkboxs(form,checkbox) { 
 
    var valor;
    if(checkbox.checked) valor = 1;
    else valor = 0;
 
        for (i=0;i<form.elements.length;i++)
    
	  if(form.elements[i].type == "checkbox") 
             form.elements[i].checked=valor; 

}

function comprobar_checkboxs(form) { 
    
        for (i=0;i<form.elements.length;i++)           
	    if(form.elements[i].type == "checkbox")
            {
		
                check = form.elements[i];
                if(check.checked==true) return true;
            }
              
        return false;
    
}

function comprobar_campo(campo,mensaje)
{
    if(campo.value=='') {
        alert(mensaje);
        campo.style.backgroundColor='#FF8080';
        return false ; 
    }
    else
    {
        campo.style.backgroundColor='';
        return true;
    }
}