GoComics supports a limited set of HTML tags. To use any of the tags below, just copy-paste them into your GoComics comment and edit them as you like.
Personally, I find it useful to save my comment in notepad first, so if I make a mistake, I can delete the comment from GoComics, and paste in the corrected version.

Add a blank line: <br> or <p>
Add a link: <a href="http://www.yahoo.com/">yahoo</a>
Add an image: <img src="yahoo.com/img.jpg">
Putting an image inside a link: <a href="http://www.yahoo.com/"><img src="yahoo.com/img.jpg"></a>
Putting an image inside a link with a fixed width: <a href="http://www.yahoo.com/"><img src="yahoo.com/img.jpg" width="300"></a>
Putting an image inside a link
with text underneath:
<a href="http://www.yahoo.com/"><img src="yahoo.com/img.jpg"><br>picture c/o yahoo</a>
Bolding text: <b>desired text</b>
Italicize text: <i>desired text</i>

Certain characters, such as the ampersand, get interpreted as HTML code. In order to use them as-is (as literals), use the following codes.

& &amp;
< &lt;
> &gt;
space    &nbsp;

There are also certain shortcuts that GoComics supports. In general, you use these by surrounding the text with one of the symbols at each end (no spaces). However, things like the special single quote works in groups of three to create a newline.

!text! Hides the text
%text% Strips out the "%"
-text- Strikethrough
~text~ Subscript
^text^ Superscript
@text@ Smaller font
+text+ Underline
*text* Bold
<text> Hides the text
_text_ Italics