To avoid problems with both validators and browsers, always use & in place of & when writing If you receive the error "Missing a required sub-element of HEAD", check that you have included the TITLE element in the HEAD.
The TITLE element is required in all HTML documents.
Browsers often recover safely from this kind of error, but real problems do occur in some cases.
In this example, many browsers correctly convert ©=3 to ©=3, which may cause the link to fail.
In XHTML, unlike HTML, element and attribute names must be all lowercase.