Hello all,
I just got my CBSE Verification as part of my computer number application, thought I'd post it here since it may help someone out. (This process is applicable only for people who've done their Xth and XIIth in/after 2004).
The link is
Welcome to Results Archives
Go to the link, choose the appropriate year, enter your roll number (the webpages are easy to navigate), and your results will be displayed on the webpage.
Take a printout of this webpage and have it attested by a gazetted officer.
This will work as your Marksheet verification. You don't need to get a DD etc. made.
I had applied for my marksheet verification to CBSE (because I needed it to apply for a computer number) for both my X (2009) and XII(2011) results. After about a fortnight they returned my letter, DD etc. and stated that I could follow the aforementioned procedure for my verification certificate. I submitted this to DGCA and I just got my computer number a couple of days ago.
I realise now that the last paragraph is unnecessary, but meh. I hope this helps.