On what looks like line 14 (this one:)
$result=mysql_query("insert into customers(name,email,address,phone) values('','$first_name','$email','$home_address','$mobile_number')");
you have 5 values listed when you are only inserting into 4 columns. Removing the empty string for the first value should help match it up. perhaps a query error and not a session issue?