Creating or modifying minecraft mods require knowledge of game coding mechanics.
If you have no idea how to program or edit source codes for games or mods, you are advised to not even attempt it. One small slip up in the coding can permanently damage your game or your computer.
That being said, you need permission from the creator of a mod or texture pack before you can edit them. So, if you wish to modify an existing mod or texture pack, ask the original person who created it via the Minecraft forums.
Yes, you modify the .jar file. You would not be able to mod the in-browser version.
No, thats impossible, the mod could only modify new worlds that you create after you install the mod.
Nope. You HAVE to download a minecraft mod to have it.
Minecraft doesn't have an official best mod.
a mod where you can fly a plane on minecraft so get it
Mo Creatures is a modification (mod) for Minecraft. You can get this mod by downloading it from The Minecraft Forums.
One example of a superhero mod in Minecraft is Superheros Unlimited for version 1.6.4.
Just search in google 'Minecraft mod downloader'
You can get a mod to do just about ANYthing you want, just do a Yahoo/Google search for something like "minecraft mod".
The Ender Dragon is a part of Minecraft, not a mod. You probably need to update Minecraft.
You can mod minecraft in the mac.
SDK Planes Mod, I guess you could find it on Minecraft Forums