web/src/main/java/org/springframework/security/web/access/AccessDeniedHandlerImpl.java
public void setErrorPage(String errorPage) {
		if ((errorPage != null) && !errorPage.startsWith("/")) {
			throw new IllegalArgumentException("errorPage must begin with '/'");
		}

		this.errorPage = errorPage;
	}
public void setErrorPage(String errorPage) {
		if ((errorPage != null) && !errorPage.startsWith("/")) {
			throw new IllegalArgumentException("errorPage must begin with '/'");
		}

		this.errorPage = errorPage;
	}
The error page to use. Must begin with a "/" and is interpreted relative to the
current context root.

@param errorPage the dispatcher path to display

@throws IllegalArgumentException if the argument doesn't comply with the above
limitations