Keep in mind that a maximum of three ad units, three link units, and two search boxes may be placed on one page. In addition, note that every publisher is responsible for the content of a site on which their ad code is placed. If a site is found in violation of our policies, we will notify any publisher(s) whose ad code is on the site.
...
Publishers may not place more than one "large" ad unit per page. We define a "large" ad unit as any unit similar in size to our 300x600 format. For example, this would include our 300x1050 and 970x250 formats, our 750x200 and 580x400 regional formats, and any other custom sized ad with comparable dimensions.
However, keep in mind that placing the maximum number of allowed ad units on a page might result in it looking cluttered. Read our optimization guidelines for tips on where to place your ads. For best practices on custom sized ad units, review our custom-sized ad units page.
The above ad limits also apply to mobile sites. In addition, two or more AdSense ads may not appear on the screen at the same time on a mobile site.
