Thank you for this, but is there not a simpler way to create a path to my master CSS file sitting in the /root folder for the whole web site and use the same CSS styles? And I did test your changes and I don't see where to access those styles in the Power CMS edit window.

I'm not seeing the new classes in either of your XML files.
If you have already placed the styles in your CMS/css/cms_styles.css stylesheet, then you just need to add the class names into these two xml files:
HTMLEditor/custom/contents_insert_ContentValueStyles1.xml
HTMLEditor/custom/contents_update_ContentValueStyles1.xml
Each style name appears twice in a style block in the form of:
<Style name="myStyle" element="span">
<Attribute name="class" value="myStyle"/>
</Style>
So if (for instance) you have two classes called .firstStyle and .secondStyle, then your xml files would look like:
<?xml version="1.0" encoding="UTF-8"?>
<Styles>
<Style name="firstStyle" element="span">
<Attribute name="class" value="firstStyle"/>
</Style>
<Style name="secondStyle" element="span">
<Attribute name="class" value="secondStyle"/>
</Style>
</Styles>
Note: Don't include the dot before the class name in the xml blocks.
