public void updaterating(List<Opportunity> oppor)
{
    Map<Id,Account> accountMap = new Map<Id,Account>();

    for(Opportunity o : oppor){

        if(o.StageName == 'Closed Won'){
            accountMap.put(o.Id, new Account(Id=o.AccountId, rating='Hot',site = o.StageName));
        }
        system.debug('TEstKNocky' + accountmap);
    }
    //Update all the appropriate accounts in a bulkified manner here.
    if(accountMap.size() > 0)
    {
        update accountMap.values();
    }
}