[Huge difference between requests and impressions]

Thanks a lot.

Your guide let me better understand what actually is considered request and impression. 

[Huge difference between requests and impressions]

Hi,

Recently we started to note huge differences between the amounts of requests and impressions. There can event be more than twice as many requests as impressions. This problem affects only certain combinations of banners and zones. Thus:

• What can be the reason for non equal amounts of requests and impressions?
  • Is this problem on server side or something fails in the browser
• What is the typical/acceptable disproportion. (I assume there will always be some difference)
• Are there any tests we can perform to gather more data about the problem?

We are using:

Revive Adserver v3.2.1 running on Apache 2.4.7, PHP 5.5.9-1ubuntu4.11 and MySQL 5.6.10-.

I will be very grateful for any help.

--edited

Recently we even note that there are counted requests to the campaigns which invocation codes are nowhere posted.