It's also easy.
You need to include a small internal CSS (styling) that's it.
Step.1) Include in your html code this simple style(preferably inside Head tag.)
border: 2px solid green ;
Step.2) Now whatever code you want to keep inside the box. Change it to HTML entities format by processing from www.simplebits.com.
Once processed. Paste the processed code inside
tag as shown:
Your Processed Code HTML entities format
Step.3) That's it !! [Please like/share/comment if you find it useful !]