I have searched the forum for hours but can't seem to find the answer. I wish to centre and resize my gallery so it sits nicely in the middle of my webpage. Similarly to the demo gallery http://plogger.org/demo/
My page atm looks like: http://www.elationevents.com.au/photos.php
This problem is not specifically related to Plogger. To do this you'll have to work with CSS. Here's a quick and seriously dirty way of doing what you want, but I highly recommend you learn some real CSS instead of working with FrontPage. You'll have much more freedom to design awesome sites the way you want once you understand CSS.
In gallery.css find #wrapper. Change it to this: <code>#wrapper { font-family: Verdana,"Trebuchet MS",Geneva,Arial,Helvetica,SunSans-Regular,sans-serif; font-size: 10pt; position: absolute; top: 240px; left: 230px; width: 490px; }</code>
Here's your gallery.css with the changes to #wrapper made. Overwrite your existing gallery.css in plogger/themes/default/ with this one and it should work.