gistfile1.txt

// copy mailing street to contact
trigger on Account (before insert, before edit)
{
    List<Account> accounts = [SELECT ID, MailingStreet FROM Account WHERE AccountId = trigger.new];

    for(int i = 0; i < accounts.length(); i++)
    {
        Account a = accounts[i];
        List<Contact> contacts = [SELECT ID, MalingStreet from Contact WHERE AccountId = a.Id];
        for(Contact c : contacts)
            c.MailingStreet = a.MailingStreet;
            update c;
    }

}