When debuging web on ipehon via Safari, unable to see any page in Develop, and the iphone name will disappear after 5 seconds, after some research, found the solution:

Upgrade your safaria to the newest version, problem solved!! It may because the IOS's Safari is new than the Mac's.

If u have same problem that your iphone will disapear in Devlop menu after seconds, just try the upgrade.所以如果你也出现了，Develop下的iPhone几秒后消失的情况，尝试一次Safari升级。