diff --git a/test/viewport/README.md b/test/viewport/README.md
index 27eb30a..2a1c39c 100644
--- a/test/viewport/README.md
+++ b/test/viewport/README.md
@@ -7,15 +7,15 @@ in a real browser:
 make frontend-viewport-test
 ```
 
-It runs the unit tests, builds the page into `dist/`, and serves it from the
-same nginx image, with the same `configs/nginx.conf`, as the Docker image.
-Before the browser starts, it checks that `/`, and a path nginx answers with the
-page, are served with `Cache-Control: no-cache` and a `Content-Security-Policy`
-header. Then it starts a headless Chrome in a container and opens the page in it
-at each width. For each width it measures the layout inside the page and checks
-the measurements in Node. The checks decide pass or fail. Screenshots and a
-`results.json` land in `tmp/viewport/`, for a person to look at when a check
-fails.
+First it runs the unit tests. Then it builds the page into `dist/`. It serves
+`dist/` with the nginx image and the `configs/nginx.conf` that the Docker image
+ships. Before the browser starts, it fetches `/` and `/no-such-page`, which
+nginx answers with the page. Both must carry `Cache-Control: no-cache` and a
+`Content-Security-Policy` header. Then it starts a headless Chrome in a
+container and opens the page in it at each width. For each width it measures the
+layout inside the page and checks the measurements in Node. The checks decide
+pass or fail. Screenshots and a `results.json` land in `tmp/viewport/`, for a
+person to look at when a check fails.
 
 The test is not part of `make check`: it needs Docker and takes minutes, and
 `make test` has to finish in under 60 seconds.
@@ -51,7 +51,7 @@ Four more widths are fixed, each for a stated reason:
 
 ## The checks
 
-Every check runs at every width, and none stops the others.
+A failed check does not stop the others.
 
 - `app-rendered`: at least 10 WAN host rows exist, and at least 5 rows show a
   number as their latency. Without this, the other checks could pass against a
@@ -99,7 +99,7 @@ So the rows show one-, two- and three-digit latencies and some unreachable rows,
 and the layout is tested against that spread. The request to
 `http://192.168.1.1` is answered, so the `Local Gateway` row appears.
 
-On each page, the test sets the interval to 1 second and waits until at least 5
+At each width, the test sets the interval to 1 second and waits until at least 5
 rows show a latency before it measures. The page discards its first round, so
 this reaches a filled page without waiting out two rounds at 3 seconds.