In the 5.2.3 default "index" skin for DNN here's what is in place
<div class="Widgets">
<object id="SizeWidget" codetype="dotnetnuke/client" codebase="StyleSheetWidget" declare="declare">
<param name="baseUrl" value="<%= SkinPath %>css/variations/" />
<param name="template" value="<div title='{TEXT}' {ID} {CLASS}></div>" />
<param name="default" value="width1024" />
<param name="Width 1024" value="width1024" />
<param name="Width 1280" value="width1280" />
<param name="Full Width" value="widthfull" />
</object>
<object id="TextSizeWidget" codetype="dotnetnuke/client" codebase="StyleSheetWidget" declare="declare">
<param name="baseUrl" value="<%= SkinPath %>css/variations/" />
<param name="template" value="<div title='{TEXT}' {ID} {CLASS}></div>" />
<param name="default" value="MediumText" />
<param name="Small Text" value="SmallText" />
<param name="Medium Text" value="MediumText" />
<param name="Large Text" value="LargeText" />
</object>
</div>
You will want to check out the various CSS in use in that skin to fully understand how all of this works, basically CSS files get swapped out and modify the styles in place on the page.