top: OK so while developing I wasn’t able to figure out why the top property wasn’t being applied. Eventually I found out that once the position is set to static, top property will have no effect.

margin: Setting margin to “0 auto” will place the item always in the middle of the page regardless of the screen aspect ratio.

transparency: Workaround for transparency issues in IE6 is by using Microsoft’s AlphaImageLoader filter. It can only be applied to one picture at a time in CSS file so use of CSS sprite is not possible when sprited image contains transparency.

IE hacks: Working for IE only hacks use the HTML comment hack as defined like code below or you can use a CSS comment hack (compatible upto IE7).

<!--[if IE 6]>
Special instructions for IE 6 here