Special Characters
The only reason HTML codes can't be displayed in full view is because of the < and > at the beginning and end of your code. But how did I just do it? Simple.
< gives you < and > gives you >. All you have to do is change the < and > to < and > in your code and everything else will show up perfectly fine. In this case, you can also make parts of your code bold, underlined, italics etc. to emphasise certain parts of the code.
Example Tag
Another way, which is a lot faster is to use the exmaple tag. This, however, will not allow you to change certain parts of the code to highlight specific sections. You will just have to display it as is.
<xmp>Your HTML Code Here</xmp>
This doesn't go on to the next line automatically if it's wider than the page, it will just for the page to scroll. You must then figure out where you want a new line to begin and hit enter (like you would on Microsoft Word).