You can apply the user-select CSS property to an element to control how it handles selecting text for copy and paste. This allows you to limit selecting text, or make it automatic. If you use the all property, anytime a user clicks on that element the text is automatically selected. This can be useful for keys or codes where the user is expected to copy and paste the text.

.click_select { user-select: all; }

Example:

Click me!

Vim is my code editor of choice as it has great features, excellent syntax highlighting, and a robust plug-in infrastructure. I'm very used to look and feel of Vim. If you want to share some of your code online, converting things to HTML can be problematic. Luckily Vim has a built in code to HTML converter:

:TOhtml

Simply run the :TOhtml command in an open text file and your buffer will be redrawn in HTML which you can then save. Here is a quick sample of my pcg32.pl script converted to HTML.