Quote Chris1953="Chris1953"I do apologise as this site is so well known for it's correct spelling and grammar!!'"
There is no apostrophe in 'it's', as in belonging to; only when you mean 'it is'. 
For example:
Chris
=red's post was, as usual, rubbish. From 
=redits humourless tone, to 
=redits poor spelling and grammar, 
=redit's what we have come to expect from so many trolls.    
 
