How to prevent request that returns 304

Question

When does a browser NOT make a request to the server for a file?

In other words, I have a JavaScript file being served. Its HTTP response header has an ETag

Answer 1

There is a rule that setting an Expires header more than one year in the future violates the HTTP 1.1 RFC.

So, HTTP response header here is invalid (Expires: Tue, 19 Jan 2038 03:14:07 GMT). Fixing this may solve the problem!