how does google decide whether to display ads
I noticed that there are certain keywords where there are no paid results at all. Nevertheless I would think that some of those keywords are of some commercial value.
I conducted a simple experiment. I created an subpage of my application that would specifically target the keyword. I would then prepare an ad that would specifically mention the keyword and link to the subpage. Despite my best efforts I was getting an error message "Your ad is not appropriate for display in Google Search network" (no further details). I was able to target different keywords with the very same ad - even without any alterations. I also tried placing higher bids - some of them really high - it didn't affect the outcome. My experiment didn't concern anything controversial. My company sells legal services such as documents and advise.
I have the following questions:
1. How does Google decide whether to display paid ads vs organic results. It seems to me it sometimes doesn't display any ads, even when there are ads available for a particular keyword,
2. Are certain keywords classified as "not biddable" ? Note, the particular keywords I tried were not in any way controversial. I was trying to target a name of a certain legal act in Poland.
3. Is it possible that Google doesn't display an ad at all because it thinks it is irrelevant (despite there being no competition) ?
Finally, perhaps someone could point me to some resources that would discuss topics such as the above (something focused more on algorithms and experiments and less on the basics).
Re: how does google decide whether to display ads
All the selected keywords, ads and the website has to go through a rigorous Adwords policy compliance process and only the approved combinations will be eligible trigger ads.
If any of these (keywords, ads or website) found non compliant with Adwords policies, then those will be disapproved/suspended.
You can find more about Adwords policies here https://support.google.com/adwordspolicy/answer/6008942?hl=en
Another category keywords which will 'not' trigger ads even after policy approval is 'Low search volume' keywords.
These keywords with very little to no search history on Google will be inactive until its search traffic increases (For example a name of a certain legal act in Poland).
You can find more about low search volume keywords in the link below
Hope this helps,