Okay! Thanks for the link! So, how many users can buy slots simultaneously? Slot being bought by a lot of people isn't good as the site may shutdown anytime unless you refund them. Does it have any limitation? Do you refund the users whose advertisement wasn't displayed or only displayed for some time? If yes, what is the criteria of refunding the users whose advertisement was displayed for some time? How much will you deduct from it? I like to get an answer especially for the CPM model. 
~~MZ~~
~~MZ~~
Since we hold the funds from advertisement sales in escrow on our service until the publisher actually fulfills the advertisement sale if a website shuts down at some point before all of the pending inventory runs we will return the funds to the purchasers BTCAN wallet.
In the event an advertisement is terminated while running we will approach those on a case-by-case basis. Regarding CPM we would look at factors such as how much a single view would have cost and make a determination from that.
It is our hope that via our application process for determining which publishers can be on the site we can accept sites that aren't fly-by-night operations. We are evaluating things when a site applies such as how long they've been operating. We want to get to know our publishers because when they win, we win.
We are currently evaluating options regarding limitations of how far in the future an advertisement can be purchased. We are going to be doing some testing with various lengths of time but right now it appears we aren't going to allow advertisement purchases beyond 60 days in the future.