Steam toolbar

About a year ago I downloaded Steam to play games. I haven't used it for a long time so removed Steam from iMac. But every time I open Safari there is a notice that there is a toolbar or chatroom or something that is not compatible with this version of Safari.

So far I have just been closing that notice box, but it is starting to get irritating. Can someone offer suggestions to get rid of this. I thought removing the Steam program would have done that.

Thanks in advance.