In one of my blogs, I had been using the url format of http://www.mydomainname.com/index.php/2008/07/post-name . This url structure is not used by many people but somehow I used it because it wasn’t working when I tried to use the http://www.mydomainname.com/2008/07/post-name . So, I had been using this permalink style for around 2 years and I never changed it because my advertisers would simply complain that their post urls can’t be found. And it went alright until recently when wordpress 2.6 was released.
When I installed the new wordpress 2.6, this permalink is no more working and I have to change it to the more correct one – http://www.mydomainname.com/2008/07/post-name . But the problem is that if I change it, my post urls will all be changed and many advertisers won’t be able to find their posts -especially those posts which are written for advertisers. So, I had only one choice – to restore to the previous version of wordpress 2.5. For now, that is the only solution to this problem. If you are also having the same URL structure, I recommend you not to upgrade to the new version until a compatible version is released. However, I don’t think that the next version will work on this URL structure because I think they are trying to remove this structure altogether and the last option still remains the same.