[Phytrix]

Who is the original author?
And if you rewrote it in your own words you don't need to give credit, as it's technically your own work.

Thanks for the tutorial.

Not really. If you based your work off a specific source, you would still need to give credits to where you got your information from.

You don't need to, by any unwritten rule or stated one. Sure, some people choose to, and it's necessary in educational papers, although in a forum post... not really. Only if you copied a certain part or the whole thing.