Código HTML:
<!DOCTYPE html> <html lang="es"> <head> <meta charset="utf-8" /> <script> var dispositivo = navigator.userAgent.toLowerCase(); if( dispositivo.search(/iphone|ipod|ipad|android/) > -1 ){ document.getElementById("menu-desktop").style.display = "none";} else { document.getElementById("menu-portatil").style.display = "none"; } </script> </head> <body> <div id="menu-desktop">menu desktop</div> <div id="menu-portatil">menu portatil</div> </body> </html>