Eclipse:some sites could not be found. See the error log for more detail. Workaround

Today I encountered a wonderful problem, I upgraded my SDK tools version to 23, and I tried to upgrade ADT in Eclipse, and I found a problem with the following analysis:

When I select Help-->check for updates in Eclipse, a box pops up as follows:

First, explain why this error occurred :

When eclipse is check for updates, it is based on all available software sites in the list. An error occurs when a site does not exist.

Some people here may ask, I used to install the address can be used, why now the address is not. This is because some of the plugin's site address is not static.

workaround : To the first picture indicated in the non-existent address, in the second picture of the list to find, the non-existent address before the tick off or delete, this time again check for updates on the line.