function modifyFields (tag, type, fn)
{
   var fields, i;
   fields = document.getElementsByTagName (tag);
   for (i = 0; i < fields.length; i++)
   {
      if (fields[i].type == type)
      {
         fields[i].onfocus = fn;
      }
   }
}

function clearOnFocus (field)
{
   if (field.value == field.defaultValue)
   {
      field.value = '';
   }
}

window.onload = function ()
                {
                   modifyFields ('input', 'text',
                                 function () {clearOnFocus (this);});
                   modifyFields ('textarea', 'textarea',
                                 function () {clearOnFocus (this);});
                };