diff --git a/11-http/lab/explore.md b/11-http/lab/explore.md
index 2352583..18eb5dc 100644
--- a/11-http/lab/explore.md
+++ b/11-http/lab/explore.md
@@ -84,7 +84,7 @@ nothing). The file contains some standard HTTP:
 
     HTTP/1.1 200 OK
     Content-type: text/plain
-    Content-length: 18
+    Content-length: 16
     Connection: close
 
     Hello over HTTP!
@@ -145,3 +145,4 @@ Rename the file to `two.html5` (I'll explain why in a second) and restart the se
 Why did you have to rename the file? Because the browser will otherwise try and be clever if it thinks you're trying to access a file that you've just downloaded already. The server sends a `Last-modified` header, and if the browser notices you're asking for a file you have just downloaded, with the same timestamp as the HTTP header indicates, then your browser might ignore the rest of the request and not see that another header has changed. Changing the file name forces the browser to look again, as it thinks it's a different file now. Deleting the downloaded file, or editing the file on the server, would both have the same effect.
 
 There is a moral here: if you're doing web development, and you are trying to find out why a change you made isn't showing in the browser (even if you refresh the page), it might be a cache problem. On the network tab of the developer tools window, there should be a checkbox to "disable cache" which you might want to turn on in this case and reload the page again, to exclude the cache as the possible source of the problem.
+