OK. I figured it out myself, after countless hours of testing on my own. I finally realized these lines were managed by the code contained under ATO > Add HTML/CSS Inserts > CSS Inserts, as shown below:
HTML Code:
div#imagecontainer {
border-top: solid 5px #333;
border-bottom: solid 5px #333;
}
which I changed to
HTML Code:
/*
NOTE: code below is the original contained in this section. Directly below it - just outside of the closing COMMENT marker for this note - is my modified version
div#imagecontainer {
border-top: solid 5px #333;
border-bottom: solid 5px #333;
}
*/
div#imagecontainer {
border-top: solid 1px #333;
border-bottom: solid 0px #333;
}
Unless you see something here that requires further attention, please feel free to close out this post.