I deleted the http:// automatic text in the edit box and changed this line:

on 1:dialog:surf:edit:25:{ set %address $did(surf,25).text }

to:

on 1:dialog:surf:edit:25:{ set %address $iif($left($did(surf,25),7) != http://,http://) $+ $did(surf,25) }

That automatically adds http:// at the beginning if the user did not enter it themselves. Also I changed the dialog table to

dialog surf {
  title \"NouMeRo Internet eXpLoReR\"
  option dbu
  size -1 -1 135 25
  button \"*Surf*\", 23, 105 6 23 11,ok
  box \"SuRf the NeT\", 24, 2 1 132 21
  edit \"\", 25, 4 9 98 10, autohs
}

I find that this is much better.