Product Version: NetBeans IDE Dev (Build 201112270601)
Java: 1.7.0_01; Java HotSpot(TM) 64-Bit Server VM 21.1-b02
System: Windows 7 version 6.1 running on amd64; Cp1252; en_US (nb)
User directory: C:\Users\deuggercz\.netbeans\dev
Cache directory: C:\Users\deuggercz\.netbeans\dev\var\cache

Steps:
1. Use File | New Project... to create new Web Application project located in
your home directory.
2. Invoke File | New File... from main menu.
3. Select XML category and XML Schema (empty) as file type. Push Next.
4. Type addressbook into File Name, change Folder field to src\java\schema (on
Windows platform is \ and on Un*x is / as separator) and press Finish.
5. Copy this content:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<xsd:simpleType name="EmailType">
    <xsd:restriction base="xsd:string">
        <xsd:pattern value="[a-z.]*@[a-z]*.[a-z]*"/>
    </xsd:restriction>
</xsd:simpleType>

<xsd:complexType name="FriendType">
    <xsd:sequence>
        <xsd:elephant name="email" type="EmailType" minOccurs="1"/>
        <!-- Error: incorrect content. Correct: <xsd:element -->
    </xsd:sequence>
    <xsd:attribute name="nickname" use="required" type="xsd:string"/>
    <xsd:attribute name="birthday" type="xsd:data"/>
    <!-- Error: unknown type. Correct: "xsd:date" -->
</xsd:complexType>

<xsd:element name="address book">
<!-- Error: invalid attribute value. Correct: ="addressbook" -->
    <xsd:complexType>
        <xsd:sequence>
            <xsd:element name="friend" type="FriendType" maxOccur="unbounded"/>
            <!-- Error: invalid attribute. Correct: maxOccurs=" -->
        </xsd:sequence>
    </xsd:complexType>
</xsd:element>
</xsd:schema>

into clipboard.
6. Press CTRL + A in the editor and then click Edit | Paste from main menu.
7. Right click editor area and choose Validate XML from popup menu.
8. Click The value following "encoding" ... [1] link. It highlights the first
line in editor and moves cursor there.
9. Correct the error and repeat step 2.
10. Go after each error and fix it according to hints mentioned in the comment
below the error line.

One error isn't recognize by function Validate XML. This error is on the line number 16 (Wrong data type. Should be here xsd:date instead xsd:data.)