title: Consequences of changing from xhtml strict to xhtml transitional?
body: <p>I've been assigned some tasks on a website built a few years ago. The site is built with the document type "xhtml strict" and those who built it have been careful to follow the standard.</p>
  
  <p>Now the need has come up to use iframe on a few pages. Using the CMS they've chosen, it doesn't seem like there's an easy way to to change the document type for only these pages; the document type is set for all pages in one place.</p>
  
  <p>Now there's two options:</p>
  
  <ul>
  <li>Change the doctype of the entire site to "xhtml transitional", which
  allows iframe. </li>
  <li>Keep the doctype and let the few pages be invalid.</li>
  </ul>
  
  <p>I'd like to know the consequences of each option. Is there a downside to use transitional instead of strict? How bad is it to have a few pages that is invalid? I'm thinking in terms of SEO and such.</p>