Use a free program called "Tidy" to convert from HTML to XHTML.
HTML allows notation like:
<H1 class=mainTitle>
XHTML requires quotes around attribute values.
<H1 class="mainTitle">
HTML allows notation like:
<H1 class=mainTitle>
XHTML requires quotes around attribute values.
<H1 class="mainTitle">
Jim Albright
Wycliffe Bible Translators