Here are some tips submitted by forum users.
(This post replaces the old list, which was not displaying correctly.)

1. To display a picture already online:

<img src="http://www.yourimagehere.com/whatever.jpg"/>

2. To mark off someone else's text as a quotation, you can set it off with italic tags:

<i>quoted text</i>

3. To link to a web page or to a file that can be downloaded:

<a href="http://www.yourhostingaddress/directory/filename.extension" target="_blank">download</a>

Or: just post the web address for the target page, and let the forum software make it into a link automatically. Make sure to include the prefix "http://" or "https://" :

http://www.yourhostingaddress/directory/filename.extension

4. To skip a line before and after text:

<br/>your text here<br/>

5. How to indent a lengthy quotation:

<blockquote>Here's the quoted text.</blockquote>

The result looks like this:

Here's the quoted text.

6. To show text in monospaced font (typewriter-style) in a yellow box:

<pre>Here's the quoted text.</pre>

The result looks like this:

Here's the quoted text.

7. To add lists:

You want a bulleted list
<ul>
<li>Item one</li>
<li>item two</li>
<li>item three</li>
</ul>

You want a numbered list
<ol>
<li>Item one</li>
<li>item two</li>
<li>item three</li>
</ol>

Looks like:

You want a bulleted list

• Item one
• item two
• item three

You want a numbered list

1. Item one
2. item two
3. item three

8. To share a YouTube video, just post the web page URL into your message. There was formerly a feature that would automatically convert the link to a video embedded in your message, but this stopped working. But it's no big deal: the forum software will automatically make the URL into a clickable link, and people can easily click on the link to view the video.

If you type in the link as:

http://www.youtube.com/watch?v=2OAF2Gr2dbU

it will appear as:
http://www.youtube.com/watch?v=2OAF2Gr2dbU

9. To change the text color:

<font color="red">This line is in red.</font>

The result looks like this:
This line is in red.

10. How to insert a bold heading line:

<h2>Here's the header line.</h2>

The result looks like this:

Here's the header line.

If you want to choose the color of the header:

<h2><font color="blue">This header is in blue.</font></h2>

The result looks like this:

This header is in blue.

11. CSS and Javascript specifications are not supported.

12. To change the background color behind your text:

<table><tr><td bgcolor="lightblue">The background to this text is light blue.</td></tr></table>

The result looks like this:

The background to this text is light blue.