Introduction

One of the main points on which HTML5 win over XHTML2.0 is “backward compatibility”. XHTML2.0 sought to enforce well-written code by using very harsh error handling. If a page returns error based on syntax the user agent will stop parsing the code.
But the problem with this approach is that the earlier versions of HTML allows page to be rendered even if it is not a well-written, erroneous HTML code. So the Internet is full with badly written HTML. Strict error enforcement will disallow these websites to be displayed at all.
An HTML5 specification states that certain HTML tags should not be used but it is only a guideline to the HTML authors. The implementations, however, must support these tags to be backward compatible.
The tags, which are deprecated, are the following: Several tag attributes are also removed. Few of the most notable ones are
element
attribute removed
a, link
rev, charset
img
longdesc, name
html
version
th
abbr
td
scope
all block level elements
align
body
background
img
hspace, vspace
table, tr, th, td
bgcolor
table
border, cell padding, cell spacing
td, th
height, width
table
valign
HTML5 is a working draft, so these tag and attribute removal is still under discussion. They may finally get supported or be replaced by other attributes.