You've posted banners up on your site(s) and when you go and visit the page to see the shining sparkly goodness, you can't find them! Panic at the base ensues
Firstly, don't panic! Here's how to diagnose the problem:
Have you tried viewing your site in multiple browsers?
Often, certain browsers have customised settings which might interfere with what is displayed on a webpage. Previewing your site in multiple browsers is not only important for troubleshooting this kind of problem, but also for testing the general "viewability" of your site. If visitors using alternative browsers can't see your site as you intended, are you losing them before they become commission generating players?
Have you tried on different internet connections?
It might sound strange, but ISPs (internet service providers) aren't as fantastic as they lead you to believe in their marketing. Many ISPs use proxies which can be easily configured to block certain advertising.
Furthermore, ISPs might even go as far as preventing visits to certain websites. In certain countries, ISPs are forced by their governments to restrict access to certain content. Often times, simply attempting to access your site from a different location might yield interesting results and could answer your question.
Have you tried on a different PC
In most cases, this is the test which will help identify the issue, because it leads to discovery of the most common problem: software. When visiting your site from a completely different pc, it is probable the alternative device will not have the same software setup as the problem device. Normally, the culprit here comes in the form of anti-virus and firewall software.
Anti-virus software manufacturers have become desperate for market share in recent years, resulting in a push to differentiate themselves from the competition by covering all aspects of internet security. Thus, anti-virus programs now tend to cover aspects of web browsing, firewall functionality and email in addition to the software heuristic analysis.
The result: An overly cautious software setup which blocks almost everything that might possibly be vulnerable.
Now, this is generally not a bad thing, but for eCommerce it tends to be. The debate rages on forums all over and will most likely never really be solved. Anti-virus manufacturers are selling their products by boasting about its ability to block ads, saying things like "Never be bothered by another popup," and all the while publishers are crying when their profits just don't seem to pop up.
Now let's get back to how all of this affects you. By experiencing the empty space where your ads should have been, you have now experienced what a good amount of internet users see all the time! If you have ascertained that it is software that's causing the problem, then there is very little you can do to reach those users with a similar setup. Mostly, you'll need to rely on alternative forms of advertising. Try text based advertising such as articles and (con)text(ual) links. Video and flash content hosted on known servers can also skirt these issues quite well. For example, anti-virus software will not dare block flash content served by YouTube, now would it?
Here is a list of programs known to block various kinds of web ads:
Kaspersky
Panda Security
AVG Anti-virus
Norton Anti-virus
Squid Anti-virus
Probably the biggest and most spoken about culprit is Norton Anti-virus. To put it bluntly, Norton Anti-virus might actually be the most hated anti-virus program when asking seasoned affiliates. Try doing a quick Google search on the term "Norton affiliate ads" and see what we mean.
If you wish, you can normally disable this function of your anti-virus software, but this won't really help the situation as your visitors aren't going to question the absence of ads on your website they simply won't be clicking anything. Rather remedy the situation by using alternative means as we've mentioned earlier in this article.