codice:<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Pagina senza titolo</title> <script language="javascript" type="text/javascript"> // <!CDATA[ function dropdown_onchange(v) { var index = v.selectedIndex; var t = document.getElementById("marchio_sigla"); if(index > 0) t.style.display = ""; else t.style.display = "none"; } // ]]> </script> </head> <body> <select name="dropdown" onchange="return dropdown_onchange(this)"> <option value="variante_1">non visualizza</option> <option value="variante_2">visualizza</option> <option value="variante_3">visualizza</option> </select> <input id="marchio_sigla" type="text" style="display:none;" /> </body> </html>