The Java plug-in for web browsers used by the VoxForge applet relies on the NPAPI (Netscape Plug-in API) cross platform plugin architecture.
Starting with Windows Chrome Version 42, Google has added an additional step to configuring NPAPI based plugins like Java to run:
(Note: Chrome NPAPI support was removed from the Linux platform starting with Chrome version 35)
You can still use: Firefox, Internet Explorer or Safari.
Update - Sept 15, 2015, from Google website:
To make browsing with Chrome safer, faster, and more stable, we stopped allowing NPAPI plugins on September 1, 2015.
Plugins that use NPAPI, including Silverlight, Java, and Unity, won’t work.