function cambia_clase (cosa, estilo)
{  cosa.className = estilo;
} 

//Esta funcion se usa para verficar que un email sea valido
function verifica_email( valor)
{  var EmailOk  = true;
   var Temp     = valor;
   var AtSym    = Temp.indexOf('@');
   var Period   = Temp.lastIndexOf('.');
   var Space    = Temp.indexOf(' ');
   var Slash = Temp.indexOf('/');
   var Length   = Temp.length - 1;   // Array is from 0 to length-1

   if ((AtSym < 1) || (Period <= AtSym+1) ||  (Period == Length ) || (Space  != -1) || (Slash != -1))
   {  EmailOk = false;
   }
   return EmailOk;
}

function abre_ventana (sitio,alto,ancho)
{ var tira = "toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,resizable=0,width=" + ancho +",height=" + alto; 
		window.open (sitio,"adicional",tira); 
}
		
/*  Estas funciones fueron tomadas del sitio http://www.webreference.com/dhtml/diner/realpos4/ */
function DL_GetElementLeft(eElement)
{
   if (!eElement && this)                    // if argument is invalid
   {                                         // (not specified, is null or is 0)
      eElement = this;                       // and function is a method
   }                                         // identify the element as the method owner

   var DL_bIE = document.all ? true : false; // initialize var to identify IE

   var nLeftPos = eElement.offsetLeft;       // initialize var to store calculations
   var eParElement = eElement.offsetParent;  // identify first offset parent element

   while (eParElement != null)
   {                                         // move up through element hierarchy

      if(DL_bIE)                             // if browser is IE, then...
      {
         if( (eParElement.tagName != "TABLE") && (eParElement.tagName != "BODY") )
         {                                   // if parent is not a table or the body, then...
            nLeftPos += eParElement.clientLeft; // append cell border width to calcs
         }
      }
      else                                   // if browser is Gecko, then...
      {
         if(eParElement.tagName == "TABLE")  // if parent is a table, then...
         {                                   // get its border as a number
            var nParBorder = parseInt(eParElement.border);
            if(isNaN(nParBorder))            // if no valid border attribute, then...
            {                                // check the table's frame attribute
               var nParFrame = eParElement.getAttribute('frame');
               if(nParFrame != null)         // if frame has ANY value, then...
               {
                  nLeftPos += 1;             // append one pixel to counter
               }
            }
            else if(nParBorder > 0)          // if a border width is specified, then...
            {
               nLeftPos += nParBorder;       // append the border width to counter
            }
         }
      }
      nLeftPos += eParElement.offsetLeft;    // append left offset of parent
      eParElement = eParElement.offsetParent; // and move up the element hierarchy
   }                                         // until no more offset parents exist
   return nLeftPos;                          // return the number calculated
}

function DL_GetElementTop(eElement)
{
   if (!eElement && this)                    // if argument is invalid
   {                                         // (not specified, is null or is 0)
      eElement = this;                       // and function is a method
   }                                         // identify the element as the method owner

   var DL_bIE = document.all ? true : false; // initialize var to identify IE

   var nTopPos = eElement.offsetTop;         // initialize var to store calculations
   var eParElement = eElement.offsetParent;  // identify first offset parent element

   while (eParElement != null)
   {                                         // move up through element hierarchy
      if(DL_bIE)                             // if browser is IE, then...
      {
         if( (eParElement.tagName != "TABLE") && (eParElement.tagName != "BODY") )
         {                                   // if parent a table cell, then...
            nTopPos += eParElement.clientTop; // append cell border width to calcs
         }
      }
      else                                   // if browser is Gecko, then...
      {
         if(eParElement.tagName == "TABLE")  // if parent is a table, then...
         {                                   // get its border as a number
            var nParBorder = parseInt(eParElement.border);
            if(isNaN(nParBorder))            // if no valid border attribute, then...
            {                                // check the table's frame attribute
               var nParFrame = eParElement.getAttribute('frame');
               if(nParFrame != null)         // if frame has ANY value, then...
               {
                  nTopPos += 1;              // append one pixel to counter
               }
            }
            else if(nParBorder > 0)          // if a border width is specified, then...
            {
               nTopPos += nParBorder;        // append the border width to counter
            }
         }
      }

      nTopPos += eParElement.offsetTop;      // append top offset of parent
      eParElement = eParElement.offsetParent; // and move up the element hierarchy
   }                                         // until no more offset parents exist
   return nTopPos;                           // return the number calculated
}