On front page only the calendar plugin errors occurred.
[/plugins/calendar.plugin.php]
Line 540 (both parameters obsolete
delete callspacing="0"
rename summary to title
Line 555
delete abbr="[abbr]"

On InSkin login page 2 errors
1. error: Bad value for attribute action on element form: Must be non-empty.
From line 161
<form id="login_form" class="bComment " method="post" action="">

Resolution: inc/_core/_template.funcs.php (@version $Id: _template.funcs.php
function display_login_form( $params )
Line 2235 empty 'form_action'=>; modified to NULL

2. error: Attribute tag not allowed on element input at this point.
From line 177, column 58; to line 177, column 166

Resolution
Unacceptable {tag} attribute inside {input} tag
file [/inc/core/ui/forms/_form.class.php]
Lines: 2935, 3694, 3698

change 'tag' to 'data-tag'
see http://help.simplytestable.com/errors/html-validation/attribute-x-not-allowed-on-element-y-at-this-point/

Once logged in: No errors on single or main posts disp