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IE 6 is not displaying PNG files with full transparency
Article: P3091

The information in this article applies to:

Product: ToolBook
Component: PNG Support
Product version(s): ToolBook 9.5 +

PROBLEM
When viewing a PNG file within my exported DHTML content, the transparency of the PNG is not working properly in Internet Explorer 6, though it works fine in Internet Explorer 7, and other browsers. The problem is that a light gray mat seems to be showing behind my PNG.

INFORMATION
Internet Explorer 6 does not officially support alpha-channel type transparency for PNG images. Microsoft did not officially add support for this until version 7 of Internet Explorer. This shortcoming of Internet Explorer 6 reveals itself as a light gray mat showing behind the PNG.

However Microsoft did provide the developer community with a workaround which allows the alpha-channel type transparency for PNG images to display properly in IE 6, in most cases.

This workaround was added to SP1 of ToolBook 9.5 (and higher)

Any PNG images shown within the Reusable Graphics Placeholder or Image Object or as a graphic applied to a button - and exported from the SP1 version of 9.5 (or higher) will take advantage of the workaround Microsoft recommended and therefore should properly display the transparency for the PNG, in Internet Explorer 6.

EXCEPTIONS
There have been reported cases where some PNGs still failed to display properly in Internet Explorer 6. The specific reasons are unknown, but may include: 

  • limitations of the Microsoft workaround
  • the use of an older version of Internet Explorer 6 (ensure your Internet Explorer 6 is fully updated)

SumTotal has no plans to continue to investigate ways of adjusting the behavior of Internet Explorer 6, primarily because Internet Explorer 6 was released over 10 years ago (2001), and the number of individuals using Internet Explorer 6 is very low, and shrinking every day.



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