Elements/Attributes not allowed in xHTML Strict

• font
• center
• iframe
• strike
• u
• s
• dir
• noframes
• align
• target
• language (script)
• background
• bgcolor
• noshade
• border (allowed in table)
• height (allowed in img and object)
• width (allowed on img, object, table, col, and colgroup)
• nowrap
• text (body)
• alink (body)
• vlink (body)
• link (body)
• vspace

For more, go to:

http://24ways.org/advent/transitional-vs-strict-markup

http://liorean.web-graphics.com/xhtml/comparison.loose-strict.html

http://www.zvon.org/xxl/xhtmlReference/Output/comparison.html