What is Master Password for the Software Security Device?
This is a feature of Firefox, not Foxmarks. Firefox allows you to set a master password to protect all of your web passwords, including your password for your Foxmarks account. If you’ve enabled Firefox’s Master Password, Firefox will ask you to supply this password in each Firefox session the first time that Foxmarks tries to sync. If you don’t need to protect access to your passwords, disable the Master Password by going to Tools / Options / Security / Passwords in Firefox and click to remove the check-mark in the box “Use a master password.” If you need to keep your passwords secure (because, for instance, other people have physical access to your computer), you might consider disabling Foxmarks’ automatic synchronization by going to Tools / Foxmarks / Settings… and unchecking the checkbox.