Forum Friendly URLs and SEO
 

I am on the verge of upgrading to version 4, I have installed a test version and trying to understand the Friendly URLs.

The standard URLs have this form: /forum/showthread.php?t=17711
And Basic Friendly URLs have this form: /forum/showthread.php?17711-Thread-Name

The installation defaulted to Basic Friendly URLs which is different from 3.8.x

So what happens to site rankings and search engine indexing when overnight, after the upgrade, all URLs have changed? Did anyone experience a change in indexed pages or trafic after the upgrade?

From the SEO point of view, which of the four options for Friendly URLs is preferable? (The Mod Rewrite Friendly URLs option does not work, by the way).

I also noticed that changing a thread name is getting reflected in the URL (with Basic Friendly URLs), and the old name is getting redirected to the new one. If I change the name a 100 times, is every change in thread name is saved in the database?