One of the main things that has changed is the introduction of a new system for Captcha plugins. The new Captcha plugin system of 3.0.6 allows board administrators to easily choose from a variety of Captcha options rather than just the default one we have seen since phpBB 3.0.0 (see the new system in detail here). However it means there are significant changes to styles files that must be made to accommodate this new option.
It is important to note that while 3.0.5 styles will continue to work with a 3.0.6 installation, it will be limited to the original phpBB Captcha, and is not recommended. Styles files must be fully updated in order to take advantage of the new system, as follows:
Firstly, each Captcha plugin option has its own template file. In most cases, copying the prosilver/subSilver version of the file to your style should be fine. The currently bundled (new) template files for the Captcha system are:
If you have any questions or comments about any of the required changes, please feel free to post in the Styles Support & Discussion forum.