Import from Word adds a gray line?

I'm creating Web Help, using RoboHelp 10 and Word 2010.

I have a heading style in the Word document entitled "Topic."  In RoboHelp, this is called "h2_RH". 

It works well, except that it adds a thin gray line above the heading.  Here is the HTML:

     <div style="border: none; border-top: solid #A6A6A6 1.0pt; padding: 1.0pt 0in 0in 0in;">

           <p class="h2_RH">The three most important terms</p>

     </div>

I know how to remove the line manually, but this heading appears hundreds of times in the document.  When I edit the style in the "Edit conversion settings for Word documents" box, there are no borders.  There are no gray borders in the .css file.  So where does this little border come from, and how can I prevent it from appearing?