The same as desktop -- only 3. Even if you put more than 3, only 3 will show up, the rest will have a blank spot.

The code has the ability to show mobile ads when it detects the visitor is using mobile. Thus, the mobile facility has been phased out.

(Yea, but the mobile ads look like crap and don't properly fit on oddball devices like... iPhones!)

They haven't updated the support pages since they moved the new mobile ad serving, and since I don't know for sure, I am only serving one 320x50 on the entire page.

Better safe than sorry.

> I am only serving one 320x50 on the entire page.

Me too. I thought that was the limit anyhow (I seem to recall reading that in their guidelines from a few years ago), though recently I have seen two 320x250 units being used on other sites in the top and bottom positions, so maybe things have changed?

There are two ways of serving mobile ads as far as I know; one where you deliberately place a mobile sized ad on the page (the 320x50 ad unit - this is what I do) and the limit for that was ONE per page, and it has to be either at the top or at the bottom of the page.

The other way is to use just use a regular ad unit (say a 728x90 or a 468x60) and Google will auto magically serve a mobile sized ad when they detect a mobile device. From what I have seen on my own sites, this consists of a couple of very condensed text ads, and on my iPhone, it tends to run off the right side of the page, so it looks pretty nasty. I suppose it depends on placement and CSS around the ads, but if I have to put in some kind of conditional to deal with that, I might just as well serve an ad I *know* fits. Which is what I do.

Since the second method relies on Google to change the ads depending on the device (or viewport - I dunno which they are using, actually) one would think that the 3-ads per page rule would apply. The idea is that you don't have to change anything from desktop to mobile, you just let Google handle it. So if you can have 3 ads on a page for desktop, you can have three for mobile.

But we seem to be in a transitional stage where Google doesn't entirely know what to do about mobile ads, and they have the search and other teams evangelizing Responsive Design, while they are not offering responsive ads to Advertisers or publishers.

So until they get their act together, I'm just sticking with one 320x50.

I never had to use the 320x50 mobile format. The big box image ad 300x250 looks nice and much bigger on iPhone. I notice that advertisers are now creating a mobile version of their ads. The graphic texts are legible and image graphics are pleasing to the eye.

I still haven't converted my sites to mobile. The sole purpose of doing so is the page load. But if you have a cache plugin (I use W3 Cache), the load time is almost the same as the mobile sites. I totally hate the look of mobile sites; it's so plain and boring.

My income is never affected. In fact, it goes up every month.

Thanks for those thoughts. It seems that G needs to update its terms to more clearly cover mobiles.

I too use 300x250 and they look good to me as well. The 320x50 has an appalingly low conversion rate.

One of my problems with the 300x250 is that it would come too far down the page on a phone, and I wouldn't want to put such a big ad before the content. I dunno. Probly should test it.

Here's what I do with the 300x250 on something similar to (but not) a product review.

Top of page stuff with site name and search box. Next is a 150 pic of the item with a very basic summary to the right.

Next the 300x250 ad, then just barely visible below is the start of the main article.

So the user gets a pic and the very basic taster bits about the product followed by an ad and finally just a glimpse of the main article. The mobile ad quality now is very good and just looks good.

No absolutes, but the 300x250 earns 6x that of the 320x50. In fact over the last week, when I have put two 300x250 on some mobile pages, the eCPM is within a whisker of the same format on my main site.

What I'm trying to get my head round at the moment is the difference between pages which appear in (specifically) position 1 and 2 of the SERPS (no history, no cookies, no location etc) compared to others which appear lower in the SERPS. As far as pages which appear in position 1 in the SERPS, these have a higher eCPM for the mobile pages compared to the full site. Position 2 is about the same for both and anything below tends to drop off rather dramatically.

I thinks it's all down to what the user sees when they use G on mobiles.