This is a security warning that is displayed by newer browsers.
It means that your password is being transmitted unencrypted, which means that someone "listening" to your internet connection using packet sniffing software can possibly extratc your password from the traffic.
For banking and shopping websites where babk details and account codes are being sent this is a problem and you should not continue, but for this swap site you can continue.
You should be able to continue on this warning or add the site to some sort of trusted site.
NB If we ever do ask for cash etc we will use paypal.com which will use https and so will be encrypted.
There is a yahoo answer on this here:
http://answers.yahoo.com/question/index?qid=20090430171649AATRsFn
There is a Wikipedia explanation here:
http://en.wikipedia.org/wiki/Basic_access_authentication
To get around this, just click OK to continue anyway see
http://www.pcadvisor.co.uk/forums/index.cfm?action=showthread&threadid=323290&forumid=1
Any questions ask a Computer Savvy person or send me some feedback.
-Adam