Eclipse Open XML File check error resolution

The XML file reported a checksum error in eclipse:

The content of element type "Web-app" must match "(icon?,display-name?,description?,distributable?,context-param*, Filter*,filter-mapping*,listener*,servlet*,servlet-mapping*,session-config?,mime-mapping*,welcome-file-list?, error-page*,taglib*,resource-env-ref*,resource-ref*,security-constraint*,login-config?,security-role*, env-entry*,ejb-ref*,ejb-local-ref*) "....

Web. XML Header configuration:
<?xml version= "1.0" encoding= "UTF-8"?>
<! DOCTYPE Web-app Public "-//sun Microsystems, INC.//DTD Web Application 2.3//en" "Http://java.sun.com/dtd/web-app_2_3. DTD ">

Workaround 1:

1: Rearrange in a prompt order
2: Delete <! DOCTYPE ... This section of the content
3: Turn off validation in eclipse by doing the following:
(1). Menu "Windows"-"preperences"-"Validation"
(2). Find "XML Validator" on the right, uncheck "Bulid" check box, leave "Manual" selected, because we need to ensure the correctness of XML at last, this can select "Validate" in the right-click menu by selecting the XML file. Manual to verify, if the XML is wrong, will pop-up window prompt, but if the "Manual" check box is also canceled, and then manually verify, even if the XML is really wrong, it will not be correctly prompted.

Eclipse Open XML File check error resolution