How to make a site like Mylot?

You'll need to hire a programmer I think as I don't think there's a free script available similar to mylot. You could try it with a normal phpbb forum and make your own formula with a script for that forum assigning credits to the members and assign a certain value per credit. I've seen such a plugin/script years ago. I can't really help you any further than this.

This is unrealistic

Just to get a feel on how to make and manage a forum site signup for a free forum site. like forumer.com or forumotion.com they are very simple to setup and you can really learn lots of stuff how to manage a forum. and more

Hello I have started doing a simple forum using flash and php I think this would be a mamouth task because of security and storing all the data Have you had much experience programming

If you wanna create website make use of this site http://www.tucktail.com/tt/domain-hosting-plans/ , it provides nice solution & very good in service ...i used this site & create website & got nice solution ...

Mylot was custom-designed. I guess it was created from the scratch. If you want to make a site similar with myLot, you'll need heavy knowledge on building sites. HTML and CSS won't be enough. You'll need to learn more about PHP/ASP, Javascript, JQuery, and many more. But if you happy enough with "forum script", you may want to check vBulletin or phpBB. It should be easier to be created.