For the past several months I’ve been using the WordPress default theme. During that time, I noticed my blog suddenly did not validate. I discovered that a recent WordPress upgrade modified the default theme, adding the useful, but invalid role attribute in several locations throughout the templates. That particular change surprised me, but did not negatively impact my blog.
Later, I added Google Analytics code to the default theme’s footer. Soon after, I discovered that another WordPress upgrade updated the default theme again and this time removed my Google Analytics code. This change caused the loss of several weeks of Analytics data.
I would therefore like to warn other bloggers using the default theme that the theme will be modified when WordPress is upgraded. If you want to modify the default theme in any way, be sure to create a new custom theme first. I’ve since copied the default theme to create default-modified, a new theme that includes my Google Analytics code but is otherwise identical to the default theme.