This example explains how the css is applied to the TagWidget
<div id="divId" class="tw ui-widget">
<button class="tb ui-state-default ui-corner-all">
buttonLabel <span class="ui-icon ui-icon-triangle-1-s"/>
</button>
<div class="tp ui-widget-content ui-corner-all">
<div class="tp-search">
<input class="searchInput ui-state-default ui-state-active" type="text" autocomplete="off"/>
</div>
<div class="tp-list">
<ul>
<li class="tp-tag ui-state-default" type="tag">
tagLabel
</li>
...
</ul>
</div>
<div class="tp-actions">
<ul>
<li class="tp-action ui-state-default" type="action">
actionLabel
</li>
...
</ul>
</div>
</div>
</div>