yaptığım tasarımda
The W3C Markup Validation Service da aşağıdaki hataları alıorum bu 2 hata ne demek arkadaslar çözemedim hatanın giderilmesinde yardımcı olabilecek biri varsa sevinirim
<html xmlns="http://www.w3.org/1999/xhtml">
You have used the attribute named above in your document, but the document type you are using does not support that attribute for this element. This error is often caused by incorrect use of the "Strict" document type with a document that uses frames (e.g. you must use the "Transitional" document type to get the "target" attribute), or by using vendor proprietary extensions such as "marginheight" (this is usually fixed by using CSS to achieve the desired effect instead).
This error may also result if the element itself is not supported in the document type you are using, as an undefined element will have no supported attributes; in this case, see the element-undefined error message for further information.
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The sequence <FOO /> can be interpreted in at least two different ways, depending on the DOCTYPE of the document. For HTML 4.01 Strict, the '/' terminates the tag <FOO (with an implied '>'). However, since many browsers don't interpret it this way, even in the presence of an HTML 4.01 Strict DOCTYPE, it is best to avoid it completely in pure HTML documents and reserve its use solely for those written in XHTML.