John -- there are some free sites and some are subscription.
FREE SITESFor the England and Wales Civil Registration Index of births, marriages and deaths there is Free BMD
http://www.freebmd.org.uk/ - Formal Registration of Births Marriages and Deaths in England and Wales commenced on 1 July 1837. Hence any events occurring
AFTER that date should be recorded on that site. They are recorded in quarters for each year - ie Q/E March, June, Sept and Dec.
In addition they are in 'Registration Districts' - usually this is the nearest large town to where the event took place.
Prior to 1 July 1837 we are dependant on Parish Registers for baptisms, marriages and burials.
A free site is Free Reg;
http://www.freereg.org.uk/There is also Family Search - a world wide site run by the Church of Latter Day Saints
https://familysearch.org/SUBSCRIPTION SITESThe subscription sites below include world wide records if you go for a world subscription - they include census records, civil registration indexes, many parish registers, immigration and loads, loads more.
http://home.ancestry.com/ (this is the world wide site)
http://www.findmypast.co.uk/ (there is also a World subscription on this one)
There are other subscription sites - but these 2 also have America, Australia, New Zealand etc records in their world subscriptions.
I hope this is of some help