HTML5 Image Enhancer images will not center in Bootstrap 3.
I have followed your previous suggestion about using "block-center" -->

class="img-responsive dmxHTML5ImageEnhancer center-block"

This has worked before, but for some reason it will not work on this page for with the bottom four images when viewing the "md" and "sm" sizes:
dm-webcreation.com/pc2/

Hello David,
You can't use width and height on images that have class img-responsive. You should either remove the responsive class or the width and height applied to your images...

If I remove width and length from within HTML Image Enhancer, it won't let me click on "OK" until I enter a width.

Do I remove the width and height coding directly in the Source Code?

Most probably when you added the images in DW it inserted width and height, please remove them.

I deleted this line in Source Code (Image Enhancer still demands a width for some reason): style="width:350px;height:190px;" --- but it still does not center on smaller viewports where the images stack up vertically.

Here is a strange thing:
I have two websites with almost identical coding. This one maintains the image as centered (baronremodeling.com/) -- and it actually has width and height in the Image Enhancer code:
<div class="col-md-3"> <a href="about.html" class="dmxHTML5ImageEnhancerLink"><img id="imageEnh1" src="img-thumbs/1_image.jpg" style="width:350px;height:190px;" class="dmxHTML5ImageEnhancer" alt="Learn more about Baron Remodeling & Construction" /></a>

BUT the one I am working on now (dm-webcreation.com/pc2/) refuses to center the image even when I removed width and height:
<a href="about.html" class="dmxHTML5ImageEnhancerLink"><img id="imageEnh1" src="img-thumbs/1_image.jpg" class="img-responsive dmxHTML5ImageEnhancer center-block" alt="Find out more about Platform" /></a>

Can you please remove the following rule from the supersized.css file:

* { margin:0; padding:0; }

Okay. That works and my images center nicely...
BUT!! -- Now my SuperSized background has a half-inch black margin on the right hand side (except for smaller viewports).

This will fix the issue.

ul#supersized { margin:0; padding:0; } 

Wow. Yes...it works!
Wish I had your brains for that kind of trouble-shooting!

I even put this size code back in and it still centers perfectly.
style="width:350px;height:190px;"
(Image Enhancer actually placed this code there when I used it to select the image.)