Yes! Page URL slugs (the part after the name of your website) are case sensitive and new page slugs on NationBuilder are always lowercase. But if you've send out an email or flyer or otherwise promoted a URL with uppercase or title case and it doesn't work when people try to visit your site, there is an easy fix. 

Go to your Control Panel and select your website. Under Pages > Legacy, select "New redirect" and type in a forward slash and the improperly cased portion of your URL (such as /FAQ). Then enter the proper slug for the site (faq) and save. Both versions of the URL will now work.