How did items appear in Trash when I did not trash them?

First I could not delete items in my Trash. I found info. on this site and then I could delete them.

But, I did not trash them in the first place. A bit worrying.

A few days ago I entered a reputable site, Pets at Home, a uk site. A screen appeared to tell me that I had been virused (not word for word). The screen asked me if I wanted to deal with it; cannot recall exactly the words. I pressed 'yes'. Changed my mind asap and stopped the process. Could this have caused me to find trash I had not trashed, ie, had I been got?

Also, I have FTM, ie, Family Tree Maker for Mac, geneology software. I can no longer use the menu across the top of the screen, eg, People, Place, Media, ie, drop downs to take me to options for my family trees. The mouse just cannot awake these drop downs. Do you think this may be connected?

Or is it that Yosemite is no good?

Thanks.