Of course you can job hunt (including applying and, if your medical condition permits it, attending interviews) while you're signed off as sick. It's no different to reading job ads, or visiting employment agencies, during your lunch break at work or after you've finished work.
It depends on the reason for you being 'unfit to work' and the nature of your work. If the reason for your lack of attendence at work could also apply to your job-hunting activities, then your employer (if it found out) would be perfectly entitled to ask why you hadn't offered to come back to work - perhaps on limited duties. I've disciplined a cheeky so-and-so once before because she logged herself as 'sick' but then still thought it was OK to attend the Works Xmas party.
If you are sensible about the scope of what you do, you will probably be OK.
thanks, i am off sick because of an injury at work, and i have recently had an op because of this, hopefully due back in about 3 weeks, healing is going well...aplid for jobs through computer, i can get about, but the job i do, i can't do at the moment, (physically)....