hello...im a new nokia n900 user....i cannot install .deb files...i already install rootsh....but when i type cd MyDoc on xterminal it say "cant cd to MyDoc"...any software or application i must download?.....pleasa help me....

It's not MyDoc, but MyDocs!

whenever you use command line to write paths, input the first characters and then hit the "tab" button on the screen to use the auto completion (hit twice to show all possibilities if more than one), so that you don't make typos when writting paths.

Like posted above i was too a noob in Xterminal once i started reading which is what i suggest you do it will become easier, like dude said above use TAB so much easier if you forget a command.

type this.....

cd /home/user/MyDocs

and it should take you to MyDocs directory. just typing cd MyDocs wont take you to that directory.

Just in case, once you get in the right folder do :
$ ls (to check that you are indeed in the right folder, it'll show you your deb files)
then to install :
$ dpkg -i *.deb (to install all the packages)
or
$ dpkg -i somepackage.deb (to install individual packages)

Also, you can't get .deb files that work from just anywhere. As a newbie, you are better off avoiding installing .deb files unless necessary and relying on programs like Application Manager to do your installation for you.