They probably link to a virus or malware that could hurt your blog and/or your computer. Just click on tha little trashcan icon unnerneaf an delete it. [a note, the comment could haf any name on it, not necessarily "janedoe".]
Fur tha second fing, this is why you need a backup and the Blogger Backup Utility. If your bloggie should be hijacked or deleted, an it happens, wif a backup you can easily re-create yours blog in a few minutes. Fink of all the time and hard work you's put into making your beeyouteeful blog, day after day. It makes sense to haf a backup.
Tha wonnerful cat-owned programmer, Greg, created a specshul page to show us how to download hims software, Downloading the Blogger Backup Utility 101. Then there is a page of screenshots and instrukshuns on how to setup tha program. An if that's not enuf, i'll be glad to help. Well, if i's not in tha middle of a nap. Or chasing a bug. Otherwise, i's always glad to help.
Don't furrget to take a look at the Tough-A*s-Tortie-Association's furrst efer Tortie Tummy Toosday. It's awesome, a dazzling array of tortie tummies.
Since it's also Tuxie Toosday, be sure to visit the Tuxedo Gang Hideout and see what all the tuxies are up to. Mine brofur Sol is a Tuxie-in-Training!
An tha funniest fing i's seen in a while, tha House of (Mostly) Black Cats haf a name change, hopefully not permanent, to tha House of (Mostly) Comatose Cats. Get tha "inside storie" on thems bloggie. Slackers!