firefox: improve example descriptions (#3276)

Also fix the main description to conform to the style guide.

pages/common/firefox.md

@@ -1,31 +1,31 @@
 # firefox
 
 > A free and open source web browser.
-> More information at https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options.
+> More information: <https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options>.
 
-- Open firefox at www.duckduckgo.com:
+- Launch Firefox and open a web page:
 
 `firefox {{https://www.duckduckgo.com}}`
 
-- Open it at a new window:
+- Open a new window:
 
 `firefox --new-window {{https://www.duckduckgo.com}}`
 
-- Open an incognito window:
+- Open a private (incognito) window:
 
 `firefox --private-window`
 
-- Search 'wikipedia' on your default search engine:
+- Search for "wikipedia" using the default search engine:
 
-`firefox --search {{wikipedia}}`
+`firefox --search "{{wikipedia}}"`
 
-- Launch firefox without extensions:
+- Launch Firefox in safe mode, with all extensions disabled:
 
 `firefox --safe-mode`
 
 - Take a screenshot of a web page in headless mode:
 
-`firefox --headless --screenshot {{path/to/output_file.png}}  {{https://example.com/}}`
+`firefox --headless --screenshot {{path/to/output_file.png}} {{https://example.com/}}`
 
 - Use a specific profile directory to allow multiple separate instances of Firefox to run at once: