common pitfalls when going from html to xhtml

common pitfalls when going from html to xhtml
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<img /><br /><input />     #good, bad: <img><br><input>
<i><b>hi</b></i>           #good, bad: <b><i>hi</b></i>
<a href=""></a>            #good, bad: <a href=''></a>
<a href="a=b&amp;c=d"></a> #good, bad: <a href="a=b&c=d"></a>
&#160;                     #good, bad: &nbsp;