SharePoint Stack Exchange is a question and answer site for SharePoint enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Hi I'm new to SP 2010, picking up a site someone else customized.

I opened the site's master page then followed the link to the css section to change.

Saved the change and the page looked fine. But, I went back to make another change and the original change was overwritten!

This is only 1 site, 1 master page, but i noticed something weird - there are multiple core.css files in the top-level site, all in weird randomly named folders in {top-level site}/_catalogs/theme/themed/1386CE2C/corev4-80A8FAC2.css

I'm only familiar with SP 2007 customization, so I'm not quite sure what's going on here.

Can someone try to explain or point me to a link that will help? thanks!

share|improve this question

In SharePoint 2010, the Core.CSS file is automatically generated with Themes.

The CSS base files are populated with lots of attributes that are parsed when a theme is set, thus creating a new Core.CSS file which has the elements for a specific theme dropped in.

What you're better doing, is creating a new CSS file from scratch, and filling in your customisatiosn there, then add it to the masterpage.

As a general rule, never modify anything SharePoint gives to you in the 12 hive (SharePoint Root in 2010). Changes will more often than not just be overwritten, especialyl with a service pack installation.

share|improve this answer

ahum the 14 hive ;-)

share|improve this answer
ahum, nope the core.css in 14 hive has not been modified. but i can see when i open core{randomletters}.css that there's additional CSS at the bottom. – user2330 Feb 17 '11 at 22:33

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.