The trademark symbol is a small "TM" placed next to your business name or logo to identify it as a specialized mark that should not be copied or used without permission. Trademark is literally the "mark under which you trade", thus is a symbol of the organization is represents. If another company were to use either the same mark, or one that is very similar to it, in a way that causes confusion about which organization the mark represents, then this is infringement on your trademark, and is an illegal practice (based on the laws where your business is based and being conducted). So, adding a trademark symbol after your mark is a way of giving "fair warning" to anyone who might consider trying to cause this confusion with a customer. Keep in mind though that anyone can add a TM and call a symbol or text their trademark, but if you add a registered trademark symbol, it must be registered with the USPTO to be valid. (more on that later).
To add a trademark symbol to your brand, you simple can add a small "TM" after the logo or business name text. For the textual version, the TM is usually a superscript, which is a smaller font that is raised higher than the prior text. An example of a superscript TM would be:
Super Pop RivetsTM
To write a trademark TM symbol in HTML, there are a few possible ways (but one correct one.). In the prior example, a simple <sup>TM</sup> tag was added to make the actual TM portion appear in superscript. This works ok, but a better approach is to use an actual designated TM symbol. In HTML, this is done using a ™ entity - so the same symbol using this html entity looks like this:
The Paintball Company™
This approach is the best route for HTML, since it uses a single character to represent the trademark symbol, instead of the actual T and M characters.
A similar approach to use for HTML is to use a unicode character inline. The unicode char code is U+2122, but to use in html is ™ - and only use this if your page is running unicode (utf-8 etc). If the following example works for you, then your browser supports this: (note - our html editor is apparently forcing this character back to a ™ symbol, so the following is actually that... sorry)
Retirement Homes of America™
Since many visitors to this site just want to know how to add a trademark symbol to their website, here it is big and bold!
Trademark symbol - ™ - is ™ !