Sets the transparency of the background of graph images, in percent. A value of 100 makes the background completely transparent, while a value of 0 makes it completely opaque. Making graph backgrounds transparent makes it possible to use another image, such as a logo, a gradient or a pattern as graph background. In order for 'Background Transparency' to work, 'True Color' has to be activated.
Please note: Only the Stone Steps version of the Webalizer is able to interpret this parameter.