Do I have a virus? If I click on a bookmark it jumps to a different website

There was a virus out a month or two ago, a DNS changer virus. It doesn't effect your iPad as much as it infects your router or your ISP's system. I'm unfamiliar with the method for removing it, but I'd do a search - possibly on a different computer - with y our router's make and model and 'virus' as a search term or look around on the manufacturer's site and see what fixes they recommend.

I would delete the bookmard from the ipad. Try going to the site by entering the exact url. If it doesn't happen again, then bookmark again.

I would also go to settings/safari and delete cookies and cache.

I should have said:

clear history and clear cookies and data

also check that fraud warning is turned on under security as well as java script and block pop ups.

There was a virus out a month or two ago, a DNS changer virus. It doesn't effect your iPad as much as it infects your router or your ISP's system.

Actually, RSPlug (aka DNSChanger) infected Macs, not routers or ISP's systems. (There was similar malware for Windows... that one may have been capable of infecting routers for all I know.) Also, RSPlug has been gone for more than a year, as the folks behind it were caught in 2011. The malicious DNS servers it relied on came into FBI custody at that time, and thus ended the RSPlug threat. Those servers were taken offline in July, after being run as legit DNS servers by the FBI for months... folks still infected with RSPlug found out at that time when their internet service suddenly quit working. There's absolutely no way anyone could be infected with RSPlug now.

I have recently found that when I click on a bookmark in my bookmarks bar it opens the site then jumps to another site ( which I shall not describe). My understanding is that iOS does not have viruses?

That understanding is correct. This is going to be caused by something external to your iPad. See Eliminating browser redirects and advertisements. Although that was written for Mac users, much of it is still relevant to iPad users as well.