One item that pops out for me is that you are using <blockquote><span> and <blockquote>text which was legitimate in early HTML however XHTML only allows block-level elements within blockquotes, see
XHTML 1.0 Block-Level Elements and
Why this code showing error in W3C validator? for more information. I did a quick edit and pretty print on your post and it validates for me with only errors about missing items. Unless you are planning on entering an obfuscated code contest, pretty printing is a great idea. In your sample, your entire page below the <body> tag was a single line making it much harder to locate errors.