Hostgator.com redirect and Yahoo search redirect

I use an iMAC with 10.10.5 (Yosemite)

Presently I am using Firefox, as Safari seems to be having its own issues with a redirect (Google lead services) that have made it almost unusable.

Now Firefox has a problem with two "redirects" that just hijack a web page and do a forced redirect to their page from which there is no recovery.

1 This is the worst: I have never visited this site, and I have seen references to it being a trojan, but there is an issue with hijack.  Needless to say I do not attempt any of the links on the page.  The page is HOST Gator.com website hosting, and referrs to error 403.

2  The second issue is with a redirect to the yahoo search engine.

Both these problems are driving me nuts on Firefox, such that I am about to delete it completely.

I have by the way does a full system scan with Norton Antivirus, and no issues have been identified.

Please can anyone help with any suggestions as to what may be happening here.

Jon