Well, you can have a look at the commit history to see what changes have been accepted in the past:

https://github.com/openbsd/www/commits/master

My experience is that minor improvements tend to get accepted if they come with a solid technical motivation and fits into the overall OpenBSD mindset and ecosystem. If the change is simply justified by "best practices" and is rather large, then the conservative choice of just leaving things as they are usually prevail.

For example, I think I have seen two proposals for major overhauls of the OpenBSD.org homepage by "outsiders" over the last three years or so and they were both rejected. However, as you can see by the commit log, minor improvements (including presentation ones) happen all the time.