I need a little guidance about linux partition.in this web site http://tldp.org/HOWTO/html_single/P... under "Which file systems need their own partitions?" you can see the write clearly tell an ideal linux partition.The question is if we have 40GB Hard Disk then how much space should we give using the said partition? as well it does't include "/" i.e root partition.It is correct without allowing root partition?

You generally can use only one partition for your linux system and another partition for the swap partition. It depends on how many space is needed by lets say the users. If you expect that users will store alot of data into their home directory, it's almost a good idea to use a seperat partition. By doing this, you simplify the backing up of the users data. You always need a root partition (/) because linux works without any drive letter. So every harddrive will still be shown under the root as a directory. So it's easier for the users to know, where they stored their files and it doesn't matter on which harddrive it's stored.