App can't execute client side code (JavaScript) for some users

Question

I have this app, which loads some Lists for the User to display. (This is SharePoint relevant) There is also some code which just is client-side code. Reading out an XML File for Language, Create some DOM things and stuff.

But all this code is no executed for some of the users. If I run IE with my User I see my app. If I run IE with another User who is also Site Collection Owner, the App can't execute all this code.

It needs a long of time to load the Default.aspx, too.

Answer 1

It was because of proxy settings.

I included the web-link for jquery as library. Some of the users couldn't load it because of the proxy settings.

If someone has similar problems, check these settings.