Use american english

doc/sphinx/tutorial/virtualized.rst

+
+Running Varnish in a virtualized environment
+--------------------------------------------
+
+It is possible, but not recommended for high performance, to run
+Varnish on virtualized hardware. Reduced disk- and network performance
+will reduce the performance a bit so make sure your system has good IO
+performance.
+
+OpenVZ
+~~~~~~
+
+If you are running on 64bit OpenVZ (or Parallels VPS), you must reduce
+the maximum stack size before starting Varnish. The default allocates
+to much memory per thread, which will make varnish fail as soon as the
+number of threads (==traffic) increases.
+
+Reduce the maximum stack size by running::
+
+    ulimit -s 256
+
+in the startup script.
+