They are much much less safe than a savings account. If the yield is really high, it may be because a company is going through trouble times. You should not invest just because of a high yield. You should also look at the company(s) involved and make your own decision on how solid you think that they are.

Historically corporate bonds have better returns than bank and building society deposits, but, in view of the recent economic turmoil, are corporate bond funds still a reasonably save haven for the funds of a moderately conservative saver