1. Usually the detector, or better said, the yahoo messenger detectors are working on the same identical principle and a mistake seldom appears, as they send specific packages in order to detect. One of the false results can be caused is the Yahoo server gives back a bad answer.
2. The base of the detection is specific robots and ID-s. Another cause of a false result may be due to problems the interpretation robots might have in the exact moment in which the user is checking, case which is extremely rare.
3. About the robots we have to mention that sometimes it happens that all of them can be disconnected from Yahoo, probably the result of someone restarting the server on which they were connected. The reason of this disconnection is quite ambiguous and it doesn’t depends on us. The idea is that when these rare moments happen all of them are disconnected or they get a sort of “temporary ban” and during this they will always receive an online Status for all IDs that they check.
4. During in one of the last weeks, one of the servers on which the robots were working on has physically broke down, and we had been put into the situation to give back random results until the issue was solved. The situation had been dealt with in approximately 2 hours. It is good to know though that these cases are extremely rare.
5. 
Another cause, which happens as rarely as the physical brake down of a server is the moment when the design, or something in the structure of the website is changed. This is when the server becomes slightly unstable, which puts us into the situation where we have to suspend for a couple of minutes parts of our service, or sometimes the whole detection service, until the situation is dealt with. Although this happens also during the first days after major changes have been introduced into the application, especially during the testing period.
6. Another problem could be the Yahoo Messenger client that you use. Not so long ago, the detector was working on any Yahoo Messenger version and other clients as well, like Pidgin, Trillian, Miranda, etc. Now the detector is working on a more limited range of clients and Yahoo Messenger versions. For example, the detector is working perfectly on versions including Yahoo Messenger 10.
7. Since Yahoo has made changes regarding their web messenger and now it became a part of their Yahoo Mail service our detectors are still able to show also the real yahoo status of Web Messenger users’ as well.
Unfortunately since other web messenger services like Meebo or Ebuddy are running on the old protocols detectors can’t function properly in those cases.
8. The last cause of a false result that we shall mention is that simply your Yahoo Messenger client had connected to a server that doesn’t have the vulnerability with which the detectors are working. To completely understand this aspect, we recommend reading the article in which it is explained how the detectors are working.
