Is there a way to apply a different CSS file to system pages in a SharePoint 2010 site collection? We don't want to modify the master page and weren't sure if there's any other solution. Thanks.
Update: We're using a custom page layout for our publishing pages; within this, we have some CSS files that contain custom classes but also overwrite existing SP classes. We have not touched the master page so it's using the default one that came with SharePoint.
You could create a SharePoint DelegateControl as described here https://littletalk.wordpress.com/2010/11/18/create-an-additionalpagehead-control-packed-into-a-feature-in-visual-studio-2010/ and check in your code if it runs on a page which contain "/_layouts/" in the url and if so add a reference to your custom CSS file.
A solution is to create a custom masterpage, in which you register all CSS classes needed. This way, you'll be able to use the custom masterpage on your non-system pages and the v4.master (or whatever you're using) on your system pages without having to bug with alternating css.
I personally always go with this as it garuanties me full control.
You could use the alternate css link to brand your system pages, this can be done without any custom code
