I found this occurs when the CSS has a standard reset a la Eric Meyer's. E.g.:
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
caption, thead, tfoot, th,
table, tbody, tr, td,
article, aside, canvas, details, figcaption, figure,
footer, header, hgroup, menu, nav, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
outline: 0;
font-size: 100%;
vertical-align: baseline;
}
Solution I found was to exclude the following from the reset, then Lightbox aligns on page as expected:
table, tbody, tr, td,

Hello Ian

Our product also uses css. Applying global reset settings overwrites the css of our product.|

Regards: Vulcho.

Any plans on making it compatible i use a lot of responsive designs and most come with that

i have a solution for those using the reset.css from erick meyer without modifing it

add in the css created by the lightbox

#dmxBoxWrapper table, tbody, tr, td {
	vertical-align: middle;
	margin:auto;
}

that would make it work correctly

Hello Miguel.

I will pass your CSS workarround suggestion to our developers.
If they consider as the necessery best solution it will be implemented.

Regards:Vulcho.