When we supply the user agent
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X; en-us) AppleWebKit/534.46.0 (KHTML, like Gecko) CriOS/21.0.1180.80 Mobile/9A405 Safari/7534.48.3
to our .NET 4 webforms app, the script that defines the function __doPostBack is not present on the page and thus nothing that uses it works.
If we supply any other user agent string (say, Safari) it works fine. Can someone explain this?