Structs-error 01-Document is invalid: no grammar found

A moment of cheap, the structs-config.xml file in a paragraph deleted, the results are always reported error.
Error message: Document is invalid: no grammar found
[Html]
<? Xml version = "1.0" encoding = "UTF-8"?>
<Strong> <span style = "color: # ff0000;"> <! DOCTYPE struts-config PUBLIC
"-// Apache Software Foundation // DTD Tiles Configuration 1.3 // EN"
"Http://jakarta.apache.org/struts/dtds/struts-config_1_3.dtd"> </span> </strong>
<Struts-config>
<Form-beans>
<Form-bean name = "helloForm" type = "com. mars. demo01.structs01. form. HelloForm"/>
</Form-beans>
<! -- Used to configure ActionForm -->
<Global-exceptions/> <! -- Used to configure global exceptions -->
<Global-forwards/> <! -- Used to configure global redirect -->
<Action-mappings>
<Action attribute = "helloForm" input = "/demo01/demo01_hello.jsp"
Name = "helloForm" path = "/demo01/demo01_hello" scope = "request"
Type = "com. mars. demo01.structs01. action. HelloAction" cancellable = "true">
<Forward name = "show" path = "/demo01/demo01_hello.jsp"> </forward>
</Action> www.2cto.com
 
</Action-mappings>
<! -- Used to configure Action -->
<Message-resources parameter = "com. mars. demo01.structs01. ApplicationResources"/>
</Struts-config>
Then restore to the original state, and the result is better. Therefore, this sentence cannot be deleted. I checked on the Internet and found that this is a definition format. How can this problem be solved.