problem about valid-xhtml-Collection of common programming errors

• 
  Ali Demirci
  php html facebook xhtml valid-xhtml
  I’m actually gettings these errors and I cannot let them fixed. I need some help. I can’t found anything on Google, sorry.there is no attribute “href”<div id=”audio” href=”http://domain.com/mp3/Green Day – A Quick One While Hes.there is no attribute “xid”<div style=”margin: 0px 100px;”><fb:comments xid=”music52″></fb:comments></div>element “fb:comments” undefined<div style=”margin: 0px 100px;”><fb:comments xid=”music52″></fb:comments></div>
• 
  Matthew James Taylor
  html css xhtml w3c valid-xhtml
  I know it’s wrong to put a block element inside an inline element, but what about the following?Imagine this valid markup:<div><p>This is a paragraph</p></div>Now add this CSS:div {display:inline; }This creates a situation where an inline element contains a block element (The div becomes inline and the p is block by default)Are the page elements still valid?How and when do we judge if the HTML is valid – before or after the CSS rules are applied?UPDATE: I’ve since learned

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