I have a universal mains charger for a mobile, but the plug does not fit the sockets that I have tried
Why is this?

Pic:

http://www.google.co.uk/imgres?q=universal+mains+charger&um=1&hl=en&sa=N&g bv=2&tbm=isch&tbnid=254eTCx_7OUESM:&imgrefurl=http ://www.comparestoreprices.co.uk/compare-prices/mobile-phone-mains-charger---nokia-6110-3210-3310&docid=s3BMEqpj5vSy9M&imgurl=http://www.comparestoreprices.co.uk/images/un/universal-mains-charger.jpg&w=250&h=300&ei=11HGTuLTE86b8gOO14lw&zo om=1&iact=rc&dur=248&sig=116469979721535134251&pag e=1&tbnh=154&tbnw=131&start=0&ndsp=18&ved=1t:429,r :0,s:0&tx=124&ty=62&biw=1280&bih=682
The top black one does not fit the sockets only fits in half way.