The defaultbase64web.img is generated on-the-fly on server side
by the following PHP script:

http://dev.geogebra.org/download/lib/build/mpreduce/default.img-base64.php?date=XXXXXXXX

where XXXXXXXX is the creation date of the default.img file. Please see
the kickstart.xml files in both the desktop and web projects for details.
(The kickstart.xml file in the web project should download the appropriate
base64 encoded image automatically.)

Another option to create the defaultbase64web.img file is to use the
base64 utility from Unix:

$ base64 -w0 ../../../desktop/default.img > defaultbase64web.img
