How to insert code (such as HTML, PHP, Javascript code) in your Blogger post?

The solution is simple.

1. Copy the code into your NOTEPAD
2. Use Edit->Replace (or Ctrl+H) and in find all the < and replace them with & l t ; (delete the spaces between the characters, without spaces you would just see another < here)
3. Use Edit->Replace (or Ctrl+H) and in find all the > and replace them with & g t ; (delete the spaces between the characters, without spaces you would just see another > here)
4. Copy the code from NOTEPAD into the Blogger post
5. And you are done

What have you done? The & l t ; is another way of telling the browser to shov a <.

Simple!