One of our website have a PR4 ranking currently.. Will our PR Ranking change if we change the whole lot and redesign our whole site? What about the sub links that we have, most of them are PR4 as well, will they change? Thanks!
A change in design does not affect PR.. because you will be keeping the directory structure, URLs and pages the same as before. Unless you change your pages from www.mysite.com/page1.html to www.mysite.com/page1.php , nothing will happen to your PR. However, a change in design can affect your Search Engine Rankings.
We are moving from a traditional website structure (index.html) (./about/index.html) to using the Joomla structure.. So all the sub directories and previous links will not be used anymore, it will be replaced by Joomla.. Do I need to keep these sub directories in the server or put a link in the new site?
If all of incoming links are pointed to a main page of your site, it doesn't matter if you change site structure. In case if you have some links what are pointed to inner pages, you should do a redirect to a new pages.
This has been talked about before I just can not remember the thread. But so you know as well, NEVER CHANGE YOUR URL PAGE NAMES, even if you are just going from index.html to about/index.html. If you do so I can promise you that you will lose your page rank on all inner pages that you have changed the url's for. Changing your design will not affect serps unless you do not keep the same form of optimization you had before. That said, if you only have pr 4 on inner pages then that is not a big deal because you can get that back pretty easy as long you can maintain a 5 on the homepage. I guess it depends on how important the pr is to your site.
Not necessarily, if he does it right now (before google exports PR to the toolbar database) he has to get the same PR for inner pages at the next toolbar PR update.