added a new partion hda3 and formatted in ext3, then rebooted,
after reboot I created /mnt/hda3/ and set permission to 777

however get errors when try to mount.(output at the end of this post)

--------------------------
# [~]# fdisk -l /dev/hda
---------------------------
Disk /dev/hda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hda1 * 1 13 104391 83 Linux
/dev/hda2 14 143 1044225 82 Linux swap
/dev/hda3 144 9729 76999545 83 Linux
------------------------
[~]# mount /dev/hda3 /mnt/hda3
----------------------------
mount: you must specify the filesystem type
----------------------------
[~]# mount -t ext3 /dev/hda3 /mnt/hda3
----------------------------
mount: wrong fs type, bad option, bad superblock on /dev/hda3,
or too many mounted file systems
------------------------------------------
[~]# mount
----------------------
/dev/hdb1 on / type ext3 (rw)
none on /proc type proc (rw)
usbdevfs on /proc/bus/usb type usbdevfs (rw)
/dev/hda1 on /boot type ext3 (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
none on /dev/shm type tmpfs (rw)
----------------------------


also, /mnt/hda3 is on another hd:
--------------------------------
[~]# fdisk -l /dev/hdb

Disk /dev/hdb: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hdb1 * 1 9729 78148161 83 Linux
root@um-687 [~]#

-------------------SOLVED----------------
did mkfs -t ext3 /dev/hda3 second time and it worked.
by some reason firs time mkfs did not do anything.