The Web Transceiver is ancient and insecure Java software that is no longer supported. It may not work well or at all but it's the only Web AllStar client around so give it a try. The attached PDF is the sum knowledge regarding the installation of the Web Tranceiver. If these don't work you may be out of luck. A variable alternative is IAXRPT provided the node owner/admin has given you access.
These [File:Web Transceiver Setup Help.pdf instructions] detail install and setting up Java to work with the Web Transceiver. Both Windows and Mac instructions included.