If you've got an HTC Android phone from Three and you can't browse the internet or send and receive picture or video messages, you'll need to re-enter Three's settings. Depending on which version of Android you're using, the steps vary slightly.
Press the menu button
Tap Wireless & Networks or Wireless Controls
Tap Mobile Networks or Mobile Network Settings
Tap Access Point Names
Press the Main Menu Button and tap on New APN.
Enter the following:
Press the Main Menu button and then select Save.
Find out how to bookmark My3 and Planet 3 on your HTC phone here.