One of the disappointing changes in WordPress 2.5 was the removal of category ID numbers. I thought this was just a minor oversight, but since the 2.5.1 upgrade this problem still was not addressed.
If you are looking for a category number (this is most often needed for setting up the homepage of Magazine WordPress themes), here is a really easy way you can locate it until the WordPress team adds the category number display we all took for granted before:
1) Go to Manage > Categories.
2) Hover your mouse over the category that you need the ID of.
3) Look in the lower left corner of your web browser for the ID of that category.
Here is a screenshot example:
Hopefully WordPress will again display the category ID in one of the future updates, but thankfully this workaround is really easy.
Kyle Eslick
Kyle Eslick is the founder and primary author of WordPress Hacks. You can learn more about him at KyleEslick.com or you can follow his personal tweets here.
Nice, best post I found on the subject.
If you add code of a full page template using your code ...
best collection 
Does anyone have problem after updating? in my case, my Visitor map doesn't work well after updating >.< 
very nice theme, but what exactly means wp 2.7 ready? is it compatible with the newest version of wordpress? get ...
14 feature in theme looks quite interesting but yet have problem on SEO with some theme of Wordpress. 
Nicen themes, good work :) 
There’s actually a plugin made for 2.5 that will “reveal” the IDs again. You can get it here: http://wordpress.org/extend/plugins/reveal-ids-for-wp-admin-25/
I’m pretty sure the ID omission was a design decision, not an oversight. (Since the majority of users don’t need to know the IDs, and those who really need them can get them from the URLs, as you mentioned.)
^yeah, it was a bad idea then if it was a design choice… in my case, i was using a 3-column revolution theme and for the posts not to repeat in either columns, i needed to excluded categories by indicating the category id but since the 2.5 and 2.6 upgrade, i am having a hard time doing that now…
Bingo! I am a total n00b!
Thanks for this post.