Mozilla mail Questioins?

[Asheville Joe]

For the most part, I really like Mozilla and Mozilla Mail in 
particular.  However, I've got a bunch of questions about little things 
I could use some help with.  Most are things I could do with the dreaded 
Outlook Express on Windoze.

1) Can I add buttons to the Task Bar - like go to the previous or next 
message (not just the next new message)?
2) Is there a way to convince it to take me to Galeon or Firebird 
instead of Mozilla when I click on an URL in an email?
3) Under Windows, I needed antivirus and firewall software to be safe.  
On a Linux Desktop system, what do I need to be safe?  I know most nasty 
stuff is Windows specific, but isn't there anything I should be 
concerned about?
4) Where the heck is the spellchecker that I thought was included in 1.5?

Thanks.

Joe