While the DOCTYPE declaration informs a browser to use standards mode, it will still parse the HTML according to the rules in that DTD — in this case, HTML 4.0.
Because PSGML allows you to specify only one particular SGML declaration to be used, via the sgml-declaration (or sgml-xml-declaration for XML mode), the DTDDECL catalog feature can come in handy.
因为PSGML仅允许您指定一个要使用的特定sgml声明，通过sgml - declaration(或者xml方式的sgml - xml - declaration)，就可以方便地使用DTDDECL目录特性了。
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While in Break mode, however, you are generally not allowed to change declaration statements, such as public methods, public fields, or class declarations.