Always use lowercase letters, let quotes accompany attributes: All elements and attribute names must be lowercase, and all attribute values must use double quotation marks.
Error:
That's right:
Close all elements: some elements in HTML are not necessary to be closed. When the next element starts, the previous element is automatically closed. This is not allowed in XHTML. All elements must be closed, even if there is no content (e.g.)
Error:
Item 1
That's right:
Item 1
Error:
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
That's right:
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Error:
That's right:
Error:
That's right:
Properties cannot be reduced: in HTML, some attributes can be reduced. XHTML is not allowed to do so.
Error:
That's right:
Do not use excluded elements: some elements and attributes are allowed in HTML 4.01 Transitional and XHTML 1.0 Transitional, and are not supported under XHTML 1.0 Strict (also in HTML 4.01 Strict). Like what , ALink, align, width, height (for some elements), and background.
The span element is not allowed to be missing one of the following start tags "p", "H1", "H2", "H3", "H4", "H5", "H6", "div", "pre", "Address", "fieldset", "ins", "Del"
form (the form element must exist in the container):
