EXT2-fs warning: mounting fs with errors, running e2fsck is recommended

[Tapas Mishra]

I am getting a warning
"EXT2-fs warning: mounting fs with errors, running e2fsck is recommended"
on Ubuntu 10.04 64 bit on my laptop Dell Inspiron 1440.

Following is the fdisk output

Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000080

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        2550    20482843+   c  W95 FAT32 (LBA)
/dev/sda2            2551        5099    20474842+   7  HPFS/NTFS
/dev/sda3            5100       38913   271610924+   f  W95 Ext'd (LBA)
/dev/sda5            5100       15298    81923436    7  HPFS/NTFS
/dev/sda6           15299       15541     1951866   83  Linux
/dev/sda7           15542       15784     1951866   82  Linux swap / Solaris
/dev/sda8           15785       21342    44642578+  83  Linux
/dev/sda9           21583       26771    41680611   83  Linux
/dev/sda10          26772       31370    36933435    7  HPFS/NTFS
/dev/sda11          31632       34242    20972826    b  W95 FAT32
/dev/sda12          34243       34836     4763272    b  W95 FAT32
/dev/sda13          34837       38739    31350816   83  Linux
/dev/sda14          38740       38913     1397623+  82  Linux swap / Solaris
/dev/sda15          21342       21582     1929216   82  Linux swap / Solaris



What could be the possible cause of warning?

-- 
Tapas