Merge pull request #1511 from jeysal/master

Multithreaded web server: explain unexpected browser behavior

Author: steveklabnik

2018-edition/src/ch20-02-multithreaded.md

@@ -1126,6 +1126,11 @@ overloaded if the server receives a lot of requests. If we make a request to
 */sleep*, the server will be able to serve other requests by having another
 thread run them.
 
+Note that if you open */sleep* in multiple browser windows simultaneously, they
+might load 5 seconds apart from each other, because some web browsers execute
+multiple instances of the same request sequentially for caching reasons. This
+limitation is not caused by our web server.
+
 After learning about the `while let` loop in Chapter 18, you might be wondering
 why we didn’t write the worker thread code as shown in Listing 20-22.