A: 

IE is known for its problems with transparency in PNGs. There were many topics here regarding that: check for example this one.

RaYell  2009-09-06 06:03:11
The url in the post marked as answer has been obsolete.Is there another one?
Shore  2009-09-06 07:23:40
A: 

The iepngfix.htc available here supports background positioning. And even makes PNG transparency work in IE5.5!

Ben  2009-11-02 04:05:21
A: 

This was useful for me: CSS Opacity in Internet Explorer (IE)

Note the quirks and use use of the CSS "zoom" attribute. YMMV.

pst  2009-11-02 04:07:05

related questions

IE7 HTML/CSS margin-bottom bug.
IE7: header above menu
How to create an all browser-compatible hanging indent style in CSS in a span
How can you customize the numbers in an ordered list?
style.display not working in Firefox, Opera, Safari - IE7 OK
Best WYSIWYG CSS editor?
How important is W3C XHTML/CSS validation when finalizing work?
Solve the IE select overlap bug
IE8 overflow:auto with max-height
Autosizing Textarea
What is the best way to create rounded corners using CSS?
FF3 WinXP != FF3 Ubuntu - why?
Is there a business reason for striving for pure CSS layout?
How to set up a CSS switcher in ASP.NET
Setting a div's height in HTML with CSS
Wrapping lists into columns
CSS Background Color in Javascript
How can I make the browser see CSS and Javascript changes?
What sites offer free, quality web site design templates?
Can you recommend a good CSS online resource or book?
Html CSS Editor
In HTML, how to word-break on a dash?
Detecting font in JavaScript
How do you test layout design across multiple browsers/OSs?
Why doesn't the percentage width child in absolutely positioned parent work in IE7?