Fix typo in crash reports

Author: jpchase

index.src.html

@@ -1275,8 +1275,8 @@ <h3 id="crash-report">Crash</h3>
   <dfn>Crash reports</dfn> indicate that the user was unable to continue using
   the page because the browser (or one of its processes necessary for the page)
   crashed. For security reasons, no details of the crash are communicated except
-  for and a unique identifier (which can be interpreted by the browser vendor),
-  and optionally the reason for the crash (such as "oom").
+  for a unique identifier (which can be interpreted by the browser vendor), and
+  optionally the reason for the crash (such as "oom").
 
   <a>Crash reports</a> have the <a>report type</a> "crash".