How to schedule certain tasks within a webpage or blog

Hi.

I want to schedule a series of tasks to a blog where I will show the visitors a few things. For example, I want to show a message or a picture to every visitor of a particular page just for once no matter if the same visitor will come back later. Also, once this task is completed I would like to automatically activate the next task with similar function

What I do not know is where to start. I am sure that I have to do things with cookies and probably javascript is the one that can help me but I what should I do next, I don’t know. This is why I’m seeking for help.

Thanks for read that
John