While paging tags, all api (that have enough tags) fail with a 503 html error after just a few consecutive page requests. I don't know that it is limited to tags, but the behaviour seems to indicates a systemic oversight as explained below. `api.stackoverflow.com` on the other hand, behaves as expected and dutifully services consecutive page requests until the end of the response. A related concern is that any error raised as the result of an API call needs to be JSON, not HTML. It is this aspect of the errors that leads me to assume that the throttle code on the other api endpoints is not recognizing API requests. As a guard against what I have to expect, the request URL are unique and consecutive and as such do not constitute any sort of API abuse. **Expected response** notice the page, 176. GET /0.9/tags?key=qgAq_KfDu0KYzlNG-qaTuw&page=176&pagesize=100&jsonp=Soapi.jsonp._callback208 HTTP/1.1 Accept: */* Referer: http://localhost:23616/src/staggregator.htm Accept-Language: en-US User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; Tablet PC 2.0; .NET4.0C; .NET4.0E) Accept-Encoding: gzip, deflate Host: api.stackoverflow.com Connection: Keep-Alive HTTP/1.1 200 OK Server: nginx Date: Sat, 03 Jul 2010 22:01:42 GMT Content-Type: application/json; charset=utf-8 Connection: keep-alive Cache-Control: private Content-Encoding: gzip X-AspNetMvc-Version: 2.0 X-RateLimit-Max: 10000 X-RateLimit-Current: 7461 X-AspNet-Version: 2.0.50727 Content-Length: 1352 **Typical response from api endpoints != `api.stackoverflow.com`** GET /0.9/tags?key=qgAq_KfDu0KYzlNG-qaTuw&page=7&pagesize=100&jsonp=Soapi.jsonp._callback36 HTTP/1.1 Accept: */* Referer: http://localhost:23616/src/staggregator.htm Accept-Language: en-US User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; Tablet PC 2.0; .NET4.0C; .NET4.0E) Accept-Encoding: gzip, deflate Host: api.serverfault.com Connection: Keep-Alive HTTP/1.1 503 Service Temporarily Unavailable Server: nginx Date: Sat, 03 Jul 2010 22:01:14 GMT Content-Type: text/html Content-Length: 650 Connection: keep-alive <html> <head> <title>Too Many Requests - Stack Overflow</title> </head> <body style="font-family:Arial,Helvetica,sans-serif;"> <div style="margin: 0 auto; width: 960px;"> <h2 >We're sorry...</h2> <p>There are an unusual number of requests coming from this IP address.</p> <p>To protect our users, we can't process any more requests from this IP address right now.</p> <p>We'll restore access as quickly as possible, so try again soon.</p> <p>If you believe you have reached this page in error, <a href="mailto:[email protected]">contact us</a>.</p> </div> </body> </html>