You cannot use raw HTML in TrackStudio tasks and messages. The following is a short description of the basic rules and tags used in TrackStudio tasks and messages. 

Horizontal rules separate sections of text. They are inserted instead of a line containing three minus signs ("---").

This horizontal rule separates two sections of text.
This is the first section of text.
---
This is the second section of text.

To save the message history, you can quote separate remarks, marking them with the ">" symbol at the beginning of the quoted line. The quotes will be automatically highlighted with different colors depending on the level of quoting.

SomeBody wrote:

SB>>SB> Quoting level 3
SB>>SB> Quoting level 3
SB>> Quoting level 2
SB>> Quoting level 2
SB> Quoting level 1
SB> Quoting level 1
SB> Quoting level 1
Main text
Main text
Main text

Most links entered in the message text will be automatically recognized and substituted with HTML hyperlinks. Here are a few examples:

http://host.trackstudio.com/index.html
https://trackstudio.com/
ftp://ftp.any-domain.com/
file://c:/a.html
www.trackstudio.com

Just like hyperlinks referring to other network documents, e-mail addresses are automatically substituted with HTML hyperlinks:

mailto:support@trackstudio.com
support@trackstudio.com

Bullet list items are marked with an asterisk (*) for unordered and a hash (#) for ordered lists at the beginning of a line and followed by a space. You can indent using a space (spaces) to create multilevel lists.

# 1
# 2
 * 21
 * 22
  # 221
  # 222
  # 223
 * 23
# 3

You can quickly create a link to any TrackStudio task by specifying "#task_number":

Please resolve task #1, #2, #3