XHTML Validation, was does this error mean? -[RESOLVED]-

When I have things like drop down menus or Radio buttons and all the options validate fien apart from the one that is selected, it produces this message:
"The name and VI delimiter can be omitted from an attribute specification only if SHORTTAG YES is specified"

This is the line it produces it for:

HTML Code:

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<input type="radio" name="soonas" value="yes" checked />Soon As

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Yet it doesn't have any probs with this line:

HTML Code:

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<input type="radio" name="soonas" value="no" />Pre-Booking

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I figured it out, it was because I was using checked instead of checked ="checked"