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更新时间：2022-11-18 19:45:22
You can amend your !DOCTYPE declaration (i.e. DTD) to allow it, so that the [XML] document will still be valid:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
[
<!ATTLIST tag myAttri CDATA #IMPLIED>
]>
#IMPLIED means it is an optional attribue, or you could use #REQUIRED, etc.
more info here: