function valida()
{
 if ((document.formulari.nom.value=="") || (document.formulari.email.value=="") || (document.formulari.tel.value==""))
 {
  alert("Els camps marcats amb un * estan buits")
  return false	
 }

if (document.formulari.email.value.length >0)
 {
   i=document.formulari.email.value.indexOf("@")
   j=document.formulari.email.value.indexOf(".",i)
   k=document.formulari.email.value.indexOf(",")
   kk=document.formulari.email.value.indexOf(" ")
   jj=document.formulari.email.value.lastIndexOf(".")+1
   len=document.formulari.email.value.length
   
   if ((i>0) && (j>(i+1)) && (k==-1) && (kk==-1) && (len-jj >=2) && (len-jj<=3)) 
   {
	 return true; 
   }
   else 
   {
    alert("mail incorrecte:\n" + 
    document.formulari.email.value)
    return false
   }
  }
}