As has happened before with a fresh Debian install I was unable to get audio from Flash media in my browser. So for example if I visit YouTube I would be able to see stuff but not hear. This happens when Gnome system sounds are enabled. To correct this:

• Ensure that the package libesd-alsa0 is installed instead of libesd0.
• At the terminal type (as root):

gedit /etc/iceweasel/iceweaselrc

• Then change the line that reads:

ICEWEASEL_DSP="none"

to:

ICEWEASEL_DSP="esddsp"

• Restart Iceweasel and sound should be there.

For Firefox replacing Iceweasel with Firefox in the above steps should do the trick.