Step 5: Accessing and controlling the Arduino from the Web
You'll get an HTTP 504 Gateway Timeout if the Arduino is not running . Depending on your browser this is shown as a blank page or as "Gateway Timeout". In this case, make sure everything is tightly plugged in and try resetting the Arduino.
If everything works as intended, you should see a simple HTML page with three colored buttons . If you press a button, the Arduino LED should light up in the corresponding color.
Note that the URL does not depend on the current location of the Arduino. No matter if it's attached to your home network or to the LAN at your office, the URL remains the same. Just plug in the Arduino and control it with your browser.
Because typing the URL can be cumbersome, you can make use of a QR-Code generator like http://qrcode.kaywa.com/ to get a QR-Code of your Arduino's URL (example below).
Print it, stick it to your Arduino, access it with a QR-Code reader like Lynkee (iPhone), Kaywa (Symbian, Java phones) or Quickmark (Windows Mobile) and there you have a switch-less, yet conveniently controllable Arduino.
That's it! Thanks for your time.
If you got any questions or trouble debugging your setup, please let me know in the comments.