Two spaces after period killed by HTML

This MLA page talks about how single-spacing after period is becoming more common and should be considered the standard in writing: http://www.mla.org/style_faq3

I wonder if HTML helped the downfall of double-spacing after period. Before the majority of the web was created by html-generators, authors typed their content in HTML markup that ignored whitespace beyond a single space, without explicit use of a non-breaking-space code ( ).

It could be that the wealth of websites whose users's browsers refused to render more than one space helped make single-spacing more common and accepted.

An interesting aside: Wikipedia is a very specific about spacing, quoting the standard spacing after a period as 1 em. I'm always surprised when wikipedia shows me extremely well-documented details, formalities, and histories of topics that I took completely for granted.