tremendous size for ".xsession-errors"

[Deephay <tudoxxx@gmail.com>]

Greetings all,

I have a problem with my .xsession-errors file, this file will grow
tremendous size each day (956 MB today, cleared yesterday, with a 4 GB
size).
The major source of errors comes from gnash (I am using the amd64 port
which adobe flash player won't work), gnash is not matured yet and
will produce lots of error messages with certain kind of flash movies
which can be easily found on many websites, all of the messages are
logged in the .xsession-errors (millions of lines!), mplayer and other
applications produce some messages as well.
So I want to know that is there a way to turn down the verbose level
of the error log, or should I just add an entry in the crontab to
clean it every ten minutes? TIA!

Deephay