C# - Showing Special Text On Website

Assume that there is a web site which includes 3 different pages. I want to show a text one of the pages randomly, with is formatted with css.

For instance the pages are below:
hello-world.aspx
hi-sun.aspx
good-night-moon.aspx

* When John enters to the site, the text will appear on hi-sun.aspx,
* When Elmander enters to the site, the text will appear on hello-world.aspx

And when one enters the page which includes a special text, even if come again, it shouldn't appear.

Psedue Code:
if(Session["first"] == "1"){
//show the text in a random page }
else {
//text.visible = false
}

In the if block how can I supply the text in a random page. (it shouldn't appear in every page, should appear only one page).