Browser plugins and extensions that block ads have become extremely popular and are an increasing problem for publishers. Several tools that can detect the user of such software have been developed, and more and more websites detect this and request that users deactivate the ad blockers.
While many websites have been doing this for a while, it is not often a large company such as Yahoo! decides to follow suite. This is, nevertheless, the case, as users of Yahoo! Mail must now switch off any ad blockers in order to access their inbox. While this is currently a test that only affects certain users within the United States, it is probably a trend that will become increasingly popular in the time to come.