To start a line with spaces, you have to use " " when editing. You should also convert all double spaces " " to "  " if you want them to be displayed nicely.
That's how I lined things up in my profile.
The idea is that you select the PGP signed text, and then paste it into "gpg --verify". This works fine in Firefox and Chrome, but when you copy the data in IE, the clipboard version contains no \n chars. If I could have used <span> instead of <pre> this problem wouldn't have manifested. The profile editor wouldn't let me do that though.
I wish "copy" behaviour was consistant across browsers, when copying from a web page.
I'll make sure when I'm updating the CSS to leave <pre> styled the same way it is - if I change anything that messes with your formatting, let me know - I don't want to break what you've done!