Http error 403 forbidden

I need help as I use Internet Explorer and I was able to do this in the past but can not do it any longer. I use internet explorer to go into a program in which I have to sign into. Once I am in the program I try to click on a sub window to go into and it does not let me. It takes me back to a sign on screen. I am not a computer person and need help. Has anyone seen this before and can help me.

thanks,