Is your feature request related to a problem? Please describe.
It would be great if there is a bookmark button on each target, and the bookmarked targets can be reviewed later.

Describe the solution you'd like
There can be a bookmark page on the main website, which may contain bookmarks for all the courses. Each bookmarked target and/or exercise can be easily accessed from there.
For

Reproduction Steps

As a user with the unfiltered_html capability (an administrator)

Create a new certificate with either an <iframe> (say a video embed) or a <script> tag, for example: <script>alert( 'HELLO' );</script>

Expected Behavior

These tags would not be allowed in the content of the certificate because certificates are meant to be printed and scripts and (most)

The most recent full CI build (at the time of this writing) failed due to connection refused, but it was just transient (manually browsed the site and confirmed it worked). We should add some retries to the full CI's smoke test code so that these transient failures wouldn't cause full CI failures. Relevant code is [here](https://github.com/Azu