Fixed a few typo's in HSTS.

doc/cookbook_ssl.txt

@@ -92,11 +92,11 @@ presented with.
 .Can clients be forced to use HTTPS?
 
 After enabling HTTP Strict Transport Security per Virtual Server, a client
-get automatically redirected to HTTPS upon connection to HTTP. In principle
+gets automatically redirected to HTTPS upon connection to HTTP. In principle
 this equals to the match rule "Is TLS/SSL" with an external redirection.
-HSTS additionally adds a HTTP Header "Strict-Transport-Security" to the
+Additionally HSTS adds the HTTP Header "Strict-Transport-Security" to a
 secure connection which informs the browser that all other content on
-the page should be accessed over HTTPS. The max-age options defines when the
+the page must be accessed over HTTPS. The max-age options defines when the
 browser can check HTTP again.
 
 [[ssl-support]]