1.why is that the default players in linux doesn't have mp3 support??i've heard that
they need mp3(like xmms) plug-ins.what are these plug-ins??

2.I tried to compile a 2.6.14 kernel(.tar.bz2 format) referring a "How to build a
kernel" document.I configured everything(basically the default kernel of my FC3 doesn't
have support for my sis190 card) and compiled andinstalled everything according to
the instructions(like make mrproper,make menuconfig,make install,make modules_install,etc...)
)under the appropriate directories.At last when i checked the bootloader was also updated with the new kernel entry.
But when i rebooted the following error appeared:
Uncompressing Linux....OK,booting the kernel
ibm_acpi:ec object not found
RedHat nash version 4.1.18 starting
Enforcing mode requested but no policy loaded.
Halting now..
Kernel panic_not syncing:Attempted to kill init!


so what was the problem??
Can anyone tell me where to get the 2.6.14 kernel rpm for i386 for my Fc3??
Mine is Amd64 with AsusK8s motherboard.

For XMMS, I think you need a package called xmms-mp3. IIRC, it isn't included in some distros for maybe copyright reasons, or some kind of legal thing.. I can't remember the exact reason. It isn't true that all distros come without the MP3 support, Slackware for one includes it.

Add a 3rd-party repo like Livna and then do "yum install xmms-mp3", etc. See here.

They might not release a 2.6.14 kernel for FC3, since it's old. FC4 currently has 2.6.14 kernel, so you can upgrade to FC4 if you want.