Placing advertisements on other sites cannot give one advertiser an assurance that they would generate profit from those sites or not
. The website may claim that all advertisements posted on their site would be one hundred percent effective - but, in your own way, you have the option to determine whether that site can really generate profits for your company or not.
Check whether the website has some advertisers first. One way that you can determine whether a website is effective for placing your banner advertisements is when there are some advertisers willing to pay for the ad space too. If there are some advertisers, then it is one indication that they are generating revenues from the website.
Neglect those sites that have little to no advertisers investing on them. Having no investors on a site indicates that the site is not generating enough traffic or is not efficient in profiting any advertisers.
Another thing that you should look in to is if the site where you want to have your advertisement on is allowing you to view their visitor stats.
Check the visitor statistics of the website that you are planning to place your ads. It is best if you know the numbers. This means, you would have a brief idea on the number of potential visitors that you are actually dealing with. Don't just believe in a site that tells that they have been generating more than ten thousand visitors per day. If they do, just tell them to post some screenshots, or at least proof that they can attain the number of visitors a day.
If the stats that they will show you are similar to what they are saying to you, think carefully if these stats suits your standards and if it is then you can buy ads from them. It is highly advisable that you purchase small ads at first to determine if you will profit from it then you can make bigger investments afterwards. Always keep in mind that every business has its own risk, it is just a matter of realizing the odds if it will be successful or not.