Noob question about apt-get and sources.list

[Cuddles]

I have a lot of entries in my etc/apt/sources.list, and even though I haven't a clue about more than half of them, some being commented out previously by who knows who, and others, like security update lines, have been added, and then found to be faulty, so then commented out...

My issues: Is it common to be commenting out entries in the /etc/apt/sources.list? I realize that sites go up and down, and crash, and are changed to other locations, and all that, but, how do you keep track of all this...

I did a apt-get update - and got a whole screen-full of warnings, and errors in the listings...

Specifically:
ftp://ftp.gwdg.de (134.76.11.100) connection timed out...
http://people.debian.org ./sources -=- 403 forbidden
./packages and sid/i386 packages with 404 not found
http://non-us.debian.org ./sources and ./packages with 404 not found
and lastly, which I figured was an easy better comment this out...
http://www.videolan.org sources/ sources and i386/ packages with 301 moved permanently

I realize that the file /etc/apt/sources.list is the MAIN update/upgrade file for locating needed, and wanted programs, and that the file is sooooo easily updated with any editor, that can make it even easier to mess it all up. Either by accident, or by adding/commenting out entries in a kind of nilly-willy manor.

Looking over the above entries, finding all of them, except for the non-us.debian.org entry, I manually began to comment them out, with information on why and when they were commented out, then thought... Maybe, before I possibly muck things up with a update or upgrade, I might want to check beforehand....

Anyone got ideas on this subject?
Thanks to everyone,
Cuddles

[Cuddles]

I realized after sending off my original post, that I might have been a little abrupt, and missed the thought of adding the sources.list I have, this is the "proposed alteration" of the file:

# See sources.list(5) for more information, especialy
# Remember that you can only use http, ftp or file URIs
# CDROMs are managed through the apt-cdrom tool.

# Security updates for "stable"
deb http://security.debian.org stable/updates main contrib non-free
deb http://security.debian.org testing/updates main contrib non-free

# Security updates for "unstable" user inserted per SecurityHOWTO
# AptGet warnings on the below path REMOVED by user until resolved (20040109)
#deb http://security.debian.org unstable/updates main contrib non-free

# Stable
deb http://ftp2.de.debian.org/pub/debian stable main contrib non-free
deb http://ftp2.de.debian.org/pub/debian-non-US stable/non-US main contrib non-free

# Sources
deb-src http://ftp2.de.debian.org/pub/debian stable main contrib non-free
deb-src http://ftp2.de.debian.org/pub/debian-non-US stable/non-US main contrib non-free

# Testing
deb http://ftp2.de.debian.org/pub/debian testing main contrib non-free
deb http://ftp2.de.debian.org/pub/debian-non-US testing/non-US main contrib non-free

# Sources
deb-src http://ftp2.de.debian.org/pub/debian testing main contrib non-free
deb-src http://ftp2.de.debian.org/pub/debian-non-US testing/non-US main contrib non-free

# Unstable
deb http://ftp2.de.debian.org/debian unstable main contrib non-free
deb http://ftp2.de.debian.org/debian-non-US unstable/non-US main contrib non-free

# Sources
deb-src http://ftp2.de.debian.org/debian unstable main contrib non-free
deb-src http://ftp2.de.debian.org/debian-non-US unstable/non-US main contrib non-free

# Experimental
deb http://ftp2.de.debian.org/debian ../project/experimental main contrib non-free
deb-src http://ftp2.de.debian.org/debian ../project/experimental main contrib non-free

# Package and Software Specific
# DVD
#    currently getting a 301 moved permanently message (commented out 20040109)
#deb http://www.videolan.org/pub/videolan/debian $(ARCH)/
#deb-src http://www.videolan.org/pub/videolan/debian sources/

# Mozilla
deb http://non-us.debian.org/~kitame/mozilla ./
deb-src http://non-us.debian.org/~kitame/mozilla ./

# GNOME 2.0
# deb http://www.gnome.de/debian/ ./

# KDE 3
# deb http://ktown.kde.org/~nolden/kde stable main
# deb-src http://ktown.kde.org/~nolden/kde stable main
# We get packages from testing/unstable for now

# cdbakeoven
# deb http://coyote.asoc.euitt.upm.es/mud/debian/ ./

# XFree 4.2/4.3
#    currently getting a 404 not found message (commented out 20040109)
#deb http://people.debian.org/~branden/packages sid/i386/
#deb-src http://people.debian.org/~branden/packages sid/source/
# below was already commented out
# deb http://www.penguinppc.org/~daniels/sid/i386 ./
# deb-src http://www.penguinppc.org/~daniels/sid/source ./

# Java
#    currently getting a connection timed out message (ip=134.76.11.100) (commented out 20040109)
#deb ftp://ftp.gwdg.de/pub/languages/java/linux/debian woody main non-free
#deb-src ftp://ftp.gwdg.de/pub/languages/java/linux/debian woody main non-free
#deb ftp://ftp.gwdg.de/pub/languages/java/linux/debian unstable main non-free
#deb-src ftp://ftp.gwdg.de/pub/languages/java/linux/debian unstable main non-free
# below was already commented out
# deb http://people.debian.org/~sgybas/jdk13

# LyX & others (now in debian/unstable)
# deb ftp://ntama.uni-mainz.de/pub/debian unofficial/
# deb-src ftp://ntama.uni-mainz.de/pub/debian unofficial/

# Evolution
#deb ftp://ftp.ximian.com/pub/debian stable main
#deb-src ftp://ftp.ximian.com/pub/debian stable main

# Blades Repository (pppoeconf & co)
#    currently getting a  message (commented out 20040109)
deb http://people.debian.org/~blade/testing ./
deb-src http://people.debian.org/~blade/testing ./

# Wine CVS snapshot
# deb http://people.debian.org/~andreas/debian wine main
# deb-src http://people.debian.org/~andreas/debian wine main

# deb cdrom:[Debian GNU/Linux 2.2 r3 _Potato_ - Official i386 Binary-1 (20010427)]/ unstable contrib main non-US/contrib non-US/main

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hopefully, this works, I am still learning the interface here,
Cuddles[/code]