• Browsers cache the content.
• The cache key is based on URL and other headers defined in Vary header
• Nette send different content for the same URL, detection is done by XHttpRequestWith header.

We must add Vary header, which tells the browser that the cache should depend on XHttpRequestWith header.

vojtech-dobes/nette.ajax.js@07f03cc

Related bug in Firefox (months ago fixed): https://bugzilla.mozilla.org/show_bug.cgi?id=633743