It's probably something related to a CSS style you made on td a without using a parent. This is why it's important to use a wrapper class when styling many children, like table cells. For example:
<style type="text/css">
.my-table td a { padding: .1em; }
</style>
<table class="my-table">
<tbody>
<tr>
<td>
<a href="bob.htm">BOB</a>
</td>
</tr>
</tbody>
</table>
Then again, looking it over, it might be a style edit you made to ui-state-highlight. If so, just change your line to something like div:not(.ui-datepicker) .ui-state-highlight.
As for jQueryUI's class name calls for datepicker:
a: anchor for today is:
.ui-state-highlight, .ui-widget-content .ui-state-highlight, .ui-widget-header .ui-state-highlight
.ui-state-active, .ui-widget-content .ui-state-active, .ui-widget-header .ui-state-active
.ui-state-default, .ui-widget-content .ui-state-default, .ui-widget-header .ui-state-default
.ui-datepicker td span, .ui-datepicker td a
- td: for table cell of today:
td astyle in your css. Make sure to include a parent when CSSing table elements. Likeidyour table and CSS it by id of table or a wrapper div with a class name, or something.