FCKeditor offers you a possibility to view to the text you have written in the editing area in the HTML code. In order to view the HTML code press 
button on the toolbar.
Example:
Text written in the editing area:
This is my standard text written in the FCKeditor.
After pressing button we can see the HTML code:
<p>This is my standard text written in the <a href="http://www.fckeditor.net">FCKeditor</a>.</p>
If you want to go back to the normal text just press again.
Editing the code in the HTML language is a very difficult feature and it should only be done by advanced users. If you don't have experience in HTML type the text normally.