Hi, there’s no built-in way to restrict characters in page names since we worked hard to allow all characters to work well 
The only issue I know about is with Tomcat which is configured by default to disallow / and \ in URLs but this can be configured, see http://platform.xwiki.org/xwiki/bin/view/AdminGuide/InstallationTomcat#HAllowing222F22inpagenames
If you really really need to change that (we don’t recommend it since that will make your future upgrades harder), you could modify create_inline.vm (or override it in a custom skin) or the CreateAction.java class. But it’s not easy and I don’t know the exact places you’d need to modify (you’ll need to understand the code there).