One of the common pro-CSS arguments is that XHTML/CSS designed web sites save bandwidth since the designs don’t contain repeated use of tables, spacer gifs and other tricks to tweak layout.

So I thought it interesting that since I moved more in that direction* and also started rotating stylesheets on a daily basis, I’ve seen my bandwidth usage skyrocket per page view. Previously the bandwidth had been ~10KB/page. I started with a new CSS and it shot up to 14KB on Tuesday, then yesterday to 87KB!

This is what I have gathered:

1. Some of the increase is due to bulkier pages in general. I expanded the number of articles displayed from 10 to 15, making the index.html 8KB larger. I replaced a lightweight version of the header with the full-blown CSS c-clamp on the popular telephone pages, and the header graphic yesterday was also on the fat side at 12KB.
2. Users have to load the CSS and GIF set anew each day.
3. Users to most blogs, including this one, regularly only view one page each day, the homepage. The bandwidth savings of CSS/XHTML are thinner in these cases since you’re not benefitting from the .css being cached on subsequent pages per visit.

As an experiment I put the rotation on hold. Today, without changing a thing, the average is back down to 24KB (today’s index.html is 22KB), presumeably because yesterday’s .css and .gifs are cached in many users’ browsers. The bad news, to continue rotating the stylesheets will continue to eat up bandwidth until each theme is rotated back in again. But I’m ok with it if my service provider is.

*still nowhere near compliant, and fine with it.