Code editors word processing applications
Using word processing applications to write code is a practice that should be avoided for the following reasons:
Word processing applications have some automatic formatting built-in that will disrupt the flow of your code as you're typing. It's better to work in an environment where there is no autoformatting (unless that autoformatting is beneficial to the flow of your code in some way, but you won't find that kind of autoformatting in word processing applications anyway).
Not designed for code editing
All those great features we talked about on the Code editor features page..they don't exist in word processing applications! Word processing applications are not designed for writing code and so would not have such features. It's much more practical to use a program that was designed with those features in mind.
Annoying & unnecessary
Many word processing applications will underline (usually with a red squiggly line) words that are misspelled. A lot of your code (including HTML tags) will be underlined since word processing applications do not recognize code and will think you're typing a bunch of spelling errors. Looking at all that underlined text is annoying and unnecessary.
If you were considering a word processing application as a candidate for code editing then you shouldn't be considering it anymore. Your choices of which program to use for code editing have been narrowed!