is yahoo msngr compatible with ubuntu

the answer is yes and no.
yes if you want to install the real ym or windows live product from their respective company. however, users of ubuntu can access ym and windows live chat( r u referring to msn?) using empathy.
(applications>internet> empathy>edit>accounts).
however, sadly, empathy is resctricted to chat. if u use ym for video call or file transfer or audio call, u can use gyachoo or gyachi/e. but a quick check just now i found out that both seems not to work on maverick meerkat. just try out and see, will you?

however, if you r using it for chat only, pls use empathy bcoz it looks way way cooler than gyachi. i am not sure about windows live since i dont use it.

how what so ever, i suggest you to use skype instead., in general, no matter what os u r using, because skype support more function than ym. and fyi, ubuntu now support skype, teamviewer, adobe reader, adobe flash, java, virtual box,google chrome, audacity, vlc right from their developer! :-)

generally speaking, antivirus is not really needed for ubuntu or linux in general, because virus threat is very low, or maybe even non. linux architechture are so simple yet so strong than even if a virus has attacked it, it cant go to any other directory due to linux security architechture.google for more detail.

as for firewall, it is up to individuals,as for me, i simply dont use it.
have fun with ubuntu.

"when i see ubuntu, i see the world"

if you want some ideas of how to make your ubuntu more awesome in appearance of whatever, reply to this message.