The back of the connector looks like this:

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Pins are:

5 3 1
 4 2

From Wikipedia

The Micro-USB connector was announced by the USB-IF on January 4, 2007 and the Mini-A and Mini-AB USB connectors were deprecated at the same time. As of February 2009, many currently available devices and cables still use Mini plugs, but the newer Micro connectors are being widely adopted. The thinner micro connectors are intended to replace the Mini plugs in new devices including smartphones and personal digital assistants. The Micro plug design is rated for at least 10,000 connect-disconnect cycles which is significantly more than the Mini plug design. The Universal Serial Bus Micro-USB Cables and Connectors Specification details the mechanical characteristics of Micro-A plugs, Micro-AB receptacles, and Micro-B plugs and receptacles, along with a Standard-A receptacle to Micro-A plug adapter.

The cellular phone carrier group, Open Mobile Terminal Platform (OMTP), have recently endorsed Micro-USB as the standard connector for data and power on mobile devices. These include various types of battery chargers, allowing Micro-USB to be the single external cable link needed by some devices. As of January 30, 2009 Micro-USB has been accepted by almost all cell phone manufacturers as the standard charging port (including HTC, Motorola, Nokia, LG, Hewlett-Packard, Samsung, Sony Ericsson, Research In Motion) in the EU and most of the world. Worldwide conversion to the new cellphone charging standard is expected to be completed between 2010 to 2012.

In addition, on 22 October 2009 the International Telecommunication Union (ITU) announced that it had embraced micro-USB as the Universal Charger Solution its "energy-efficient one-charger-fits-all new mobile phone solution", and added: "Based on the Micro-USB interface, UCS chargers will also include a 4-star or higher efficiency rating—up to three times more energy-efficient than an unrated charger."