When WEBCEO scan Google it send me "Error 503 Service Unavailable". I send a request to WEBCEO support and the answer is:

• There might be a number of reasons of this issue. Let me list two most probable ones and tell you how to avoid the problem in future.

  I. Connection problem.

  When you query Google through Web CEO, your requests form a queue at a Google server. When the queue length reaches a certain size, the server stops accepting new requests, returning an error 503 (Service Unavailable). Your connection settings may have something to do with the problem.

  If you use public proxy servers from the list offered by Web CEO, please note that we take them from the free sources and cannot guarantee stable connections. If you use some proxy not from the Web CEO's list, you should ensure that it works without malfunction.

  The best way to get correct results is to take proxy settings from your browser:

  1. Open Web CEO File > Settings > General tab > Proxy and check the "Use proxy settings from Default Browser" option.

  2. Go to File > Settings > SE Requests tab > Connection - make sure that the "Use proxy servers while querying search engines" option is NOT selected.

  3. Clear the program cache (open the 'File' menu > Settings -> go to the 'SE Requests' tab -> click 'Cache'. Press the 'Clear cache' button) and re-run the task, the results should be correct.

  II. A ban from Google.

  To check if it is an IP ban, open your browser and search for something at Google. If you see a warning and a capture image (to prove that you are a human visitor), then it is a ban.

  If it was the reason of the problem, Google won't ban your IP address permanently -- it will restore your access to the services in a day. However, we believe that the default settings for the search engines requests are good enough to prevent such situations.

  I can suggest that you reduce the number of requests to Google (reduce the number of scheduled ranking tasks, decrease the number of keywords to check per run, or the number of SE results pages to scan).