Can I put html tags anywhere in my posts?
No. You can not use HTML tags in any field except in the body of the message. The maintainer of the script has the option of allowing or disallowing any HTML in the Message part of your posting. If they disallow it, the script will just throw out everything in <>'s. If they allow it, your html markup will appear in the posting. It can't hurt to try.
Why are there colons in the message when I try to post a followup?
Colons appear in the message dialog box when you try to followup up on a message to indicate that those lines are quoting the previous document. The owner of the WWWBoard can decide whether they wish to enable or disable the quoting of previous messages.
Your post should show up right away, unless you hit the "Back" button to get back to the main page. If it did not, then hit the "Refresh" button on the page, and the page will be updated.