How to write special symbol in a blog?

In order to display special characters or symbols within your HTML pages, you must use a special ASCII code in your html files. ASCII (American Standard Code for Information Interchange) is the standard format used for character within computers and online.
Here's example to create copyright information. Your HTML code might look: 
      Copyright © 2008 Company Name
The above HTML code will display like this within your web page:
      Copyright © 2008 Company Name  

To use the following symbol you can copy & paste the HTML code: 

Copyright  (©) © © 

Registered trademark sign (®) ® ®

Trademark sign (™) ™ ©

Cent sign (¢) ¢ ¢

Euro symbol (€) € 

Yen symbol (¥) ¥

Pound sterling (£) £

Degree sign (°) °

Heart symbol (♥) ♥

Pi (π) π

Less than  (<) &lt;

Greater than  (>) &gt;

If you want to see more about how to writing symbols in html, you can goto:

this link http://www.htmlcodetutorial.com/characterentities_famsupp_69.html