Today Google Adsense changes, I noticed that it is a new step of they and help their publishers have many choices ad, it is custom ad sizes.
Google said: “Custom sized ad units may have a limited inventory of display ads available, which could have a negative impact on your earnings. If your site uses responsive design, we recommend that you use a responsive ad unit instead.”
For display ads, Google system will determine the appropriate size ad to fit into the space you select; the selected ad will not be larger than the space requested, required size: 800 x 100, 300 x 400, 200 x 600.
For text ads, Google determine the optimal number of text ads to display for a given impression, and show the ads the same way they appear inside standard sizes. Google system predicts the value of each competing ad for every impression, based on historic performance and comparison across a variety of scenarios.
Google said: “For unique ad unit sizes, our system will need some time before it can optimize the number of ads shown.”