It depends on the ads clicked.

One ad may pay $4 and the next $0.04.

if thats the case then i think the 468x60 ads are better than the 120x600 because yesturday i had 468x60 and today i dont and the ads seem to be the same all the time

27 clicks and only made $0.75

how is this possible ?

27 clicks and only made $0.75 how is this possible ?

Probably your site is showing some of the pay per impression ads.

Twenty eight clicks is a small amount, and small amounts can tend to swing wide in terms of earnings and other AdSense metrics. Quite possibly the underlying problem is either the site needs more traffic or it requires a better type of traffic (for example, traffic that is looking for photos or information about celebrities tends to be garbage, along with forum traffic.).

That's ultimately, at its most fundamental level, how it works. ;)

27 clicks and only made $0.75

how is this possible ?

Well you averaged just under 2.8 cents per click. While I would have expected a higher average, even in a sample that small, there is nothing improbable about the numbers.

Where I have been able to monitor individual clicks on my site they have paid anything from 2 cents to 2 dollars with absolutely no pattern visible to me. As already noted some of the clicks could have been on ads thay pay per impression which would show in the CTR but won't earn any money. At another time you may see a payment for zero clicks for the same reason.

You may have been smart-priced.

You're clicks yesterday may have turned out to be garbage clicks that didn't convert to sales. Because of that, Google may now be smartpricing you.