Earlier today Apple released the iPhone OS 3.1.2 update, and now SDK 3.1.2 is available for developers at the iPhone Dev Center. The new version of SDK includes Xcode 3.1.2 and is compatible with both Leopard and Snow Leopard. CNET is reporting that Dashcode now supports creating Web apps "optimized for Safari on the iPhone, PC, and Mac."
Apple sent an email to developers today saying:
"Phone SDK 3.1.2 is now available on the iPhone Dev Center. If you have updated your development devices to iPhone OS 3.1.2, you will need to download and install the new iPhone SDK to continue your development."