How do you estimate the numbers of visitors and pageviews?

We use Alexa Rank to estimate traffic figures; visitors, pageviews.

How do you calculate daily, monthly revenue?

We use our traffic estimation algorithm to calculate potential advertising revenue of a website based on traffic volumes.

We recognize that every site is different and that some sites, such as ecommerce websites, may also make revenue selling goods, it would be impossible for us to know what that revenue might be. We simply show the real or potential revenue of a website that participates in display advertising.

How do you calculate the value of a website?

We use public traffic ranking data such as Moz, Google, Yahoo, Bing, Social Signals (e.g. Facebook, Google+, etc), we then combine that with Alexa Rank traffic rank statistics, advertising revenue (real or potential) and use a complex algorithm to estimate the value of a website.

We recognize that it would be impossible for any website algorithm to be able to calculate the value of a website with 100% accuracy. However, we've been doing this for a long time and strive to be able to calculate the value of any website to a reasonable degree of accuracy.