Do you mean vertically? Your gallery seems to be resizing horizontally (when I reduce my browser's width) OK.
Your gallery does not resize vertically because you have set a fixed value for your gallery's height (720px) so the gallery will be this height no matter what the size or shape of the user's browser window is.
You could try using a percentage height for your gallery if you like but you may run into problems.
In order for a gallery to resize dynamically with changes to the size of the user's browser window, the gallery's dimensions and those of all parent containers must be expressed as percentages. If there is a fixed value anywhere up the chain, then the gallery's dimensions will become fixed (for example, 100% x 100% x 800px = 800px).
In a WordPress environment where you have little or no control over the dimensions of the parent containers into which the gallery is embedded, you may not be able to guarantee that the parent containers have percentage heights or indeed have been assigned any heights at all via CSS. If this is the case, then SimpleViewer will not be able to determine what its own height should be (100% of what?) and the gallery may fail to display.
In WordPress (and other CMS environments), I would recommend setting a fixed gallery height (as you currently do).
Please see these links for further information on percentage dimensions:
FAQ: http://www.simpleviewer.net/simpleviewe … ml#embed_7
Using Percentage Heights: http://simpleviewer.net/simpleviewer/su … html#embed
SimpleViewer Support Team.