save youtube video without any software

As we all know Youtube has a very large database of videos that we watch online.
 we  love to watch videos and want to download videos to watch again and again but youtube doesn't provide any method to download video.So we always search for software .


so i found a new trick which do not need any software. 
only you have to follow following steps

THIS TRICK IS FOR MOZILLA FIREFOX...

STEP1: OPEN THE DESIRED VIDEO IN YOUTUBE, MATACAFE, OR ANYTHING ELSE..

STEP2: TYPE about:cache IN YOUR BROWSER's ADDRESS BAR

STEP3: A PAGE WILL OPEN HAVING CACHE INFO.
FROM THERE COPY THE ADDRESS OF CACHE Directory FROM "Disk cache device" SECTION
IT WILL BE LIKE SOME WHAT LIKE
C:\Documents and Settings\.......\Local Settings\Application Data\Mozilla\Firefox\Profiles\hc6pnitc.default\Cache
(SEE SCREEN SHOT)

STEP4: OPEN MY COMPUTER, PASTE ABOVE DIRECTORY ADDRESS IN ADDRESS BAR, i.e. NAVIGATE TO CACHE DIR.
THERE YOU WILL SEE MANY FILES.

STEP5: CLEARE CACHE OF UR BROWSER, NOW IN THAT FOLDER THERE WILL BE 4-6 FILES LEFT, RELOAD YOUTUBE PAGE AGAIN, N PLAY THE FULL VIDEO
U'LL SEE IN CACHE DIR. 2-3 MORE FILES ARE THERE. SO COPY THE FILE WITH LARGEST FILE, PASTE IN UR PC. N RENAME WITH EXTENSION .flv

DONE....

EVERY TIME YOU PLAY VIDEO JUS CLEAR CACHE N CHECK THE CACHE FOLDER, N COPY THE LARGEST FILE.

TO SELECT LARGEST FILE, JUS RE-ARRANGE FILES BY SIZE. N SELECT THE LAST ONE.