The standard serialisation options for an XHTML generating Xquery script are:
declare option exist:serialize "method=xhtml omit-xml-declaration=no indent=yes encoding=iso-8859-1
doctype-public=-//W3C//DTD XHTML 1.0 Transitional//EN
doctype-system=http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd'";
The html head should look like
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta content="text/html; charset=iso-8859-1" http-equiv="content-type" />
...
</head>
There is a question about the appropriate encoding - iso-8859-1, UTF-8 or nothing. There is an apparent problem with the data entry of accented characters etc when using the explicit encodings in eXist. If this is an issue, leave it out.
To suppress the addition of exist:match tags when using the free-text match operators, use the serialisation ption
highlight-matches=none