As all publishers should be aware off, Google Adsense has a lot of strict rules that they make publishers abide to and if they don’t they will find 
themselves getting banned. One of these rules is that publishers can only display a maximum of three Adsense adverts on a webpage at any given time.
Please keep in mind that a maximum of three standard ad units, three link units and two search boxes may be placed on one web page.
When I first saw this rule set out by Adsense, I thought this was pretty harsh considering the Adsense unit sizes vary considerably. Surely, it should be on the net area the Adsense adverts cover? For example, three small 125×125 units cover much less space than three 336×280 units.
There are many reasons why Adsense has put a limit on the number of adverts you can show with them being highlighted below.
- Adsense does not want to be associated with spam – The more adverts you have on a webpage, the more ‘spammy’ your website will look. This can decrease your CTR considerably and affect Adsense’s reputation of providing contextual advertising that is relevant to the web user.
- Creates a minimum competition level – If publishers were able to put as many adverts on their webpage as they want, they will find (due to the supply and demand saying) that as they increase supply of space for adverts, the demand will decrease which will result in a extremely low CPC. Therefore, having a limit on the advertising space means Adsense has created a minimum competition level for your adverts maintaining your CPC respectively.
- Keeps adverts contextual to the web user – If publishers had more than three adverts, they may find, especially if they were in a niche segment for their content, it being difficult to fill up all their advertising spaces with relevant adverts. In the end, they may find non-relevant adverts will start appearing which will produce a horrible CTR for publishers like it is with Ad Dynamo. Limiting the units on one page means each unit is guaranteed to always show relevant adverts.
The above bullet points are all valid reasons for limiting the number of adverts Adsense publishers can have on their websites. However, is that truly limiting the number of adverts publishers can have on their websites? For example, take my website AskWillOnline.com. I have a combination of Adsense adverts and BuySellAds adverts to maximise my earnings.
The problem that Adsense cannot control is that bloggers can put other forms of advertising on their website other than PPC. For me, that was banner advertising. For others, that could be banner, in-text, private or affiliate advertising.
Therefore, if Adsense were to put a maximum number of Adsense units per page to control their adverts from looking like spam, unfortunately, that is not in their control but the publisher’s control. If the publisher wants to, they can put as many adverts as they want on their website: unrelated to contextual PPC advertising.
