After installing boost, my site does no longer validate as XHTML strict. It seems there are several issues with the HTML generated by boost that the W3C Validator complains about.
First of all, the block "Boost: Pages cache status" generates the following two error messages:
Attribute "content" exists, but can not be used for this element.
document type does not allow element "form" here; missing one of "object", "ins", "del", "map" start-tag
This issues are caused by the following line of XHTML:
<span class="boost cache-status" content="7980"><small>Site Has Changed: <em>False</em><br />Expire In: <em>2 hours 13 min</em><br />Cache Generated: <em>0.65</em> seconds<br /> <form action="/" accept-charset="UTF-8" method="post" id="boost-block-flush-form">
Would it be possible to remove or change the "content" attribute and also to wrap the form properly?
The other issues are caused by the line
<iframe src="/boost-gzip-cookie-test.html" style="width:0px; height:0px; border:0px; position:absolute; top:-1000px; z-index:10;"></iframe>. Specifically, the W3C does not like:
Attribute "src" exists, but can not be used for this element.
Attribute "style" exists, but can not be used for this element.
element "iframe" undefined. Did you mean "iframe" or "frame"?
Instead of "iframe", I would suggest using "object".