Dear munirabrar,
Please follow steps:
1. Point to your css file name: <CE:Editor id="Editor1" EditorWysiwygModeCss="yourcssfile.css" runat="server" ></CE:Editor><br />
2. Create file yourcssfile.css
3.
add the following code into yourcssfile.css
hr
{
height:1px;
}
Regards,
Eric