Hello
For your background issue try removing the following from your templates styles.php (../templates/j51_nocturne/php/styles.php - line 242)..
[code type=css] -ms-filter: "progid

XImageTransform.Microsoft.AlphaImageLoader(src='<?php echo $this->baseurl ?>/<?php echo $bgimagefile; ?>',sizingMethod='scale')";
[/code]
As the template is largely CSS3 based there is some elements of the template that will appear differently on older browsers (in particular IE). Is there a specific colour you would like to use for your buttons and I will try creating the gradiant using a trident syntax (CSS which can be added to your CustomCSS field)?
Ciarán