This lawn weed is growing in Kent UK. It is very tiny, the 20p UK coin (shown in picture) is only 20mm (about three quarters of an inch) across. The plant has tiny white flowers. The photo was taken today 03 April 2014. It is not clear if this weed is simply growing amongst the lawn grass or replacing it. Extra note: the flowers are white and cup shaped.
Looks succulent, but even with clicking to enlarge several times the view isn't really close enough. Would also be better if flowers were shown.
I agree the photo is not sharp enough for confident identification, but Montia fontana (Blinks) is a possibility.
