Pop up are a function of the host server, if you can install a trigger that is activated if a reader scrolls over a particular part of your document, that is another way to accomplish the same thing. Most times pop up occur if the customer exits a page.

I am not a webmaster, these people have the knowledge that you seek.

I am not familiar with Yahoo’s site builder, but what you are talking about can be “relatively” easily achieved via a little Javascript on your web page.

For a very simple example, try modifying the source of your html page, change the tag to something like the following:

Keep in mind, this is just one way of doing it, and I don’t necessary recommend this way of doing it (For a number of reasons. For one, it isn’t a very “smart” script feature, and will appear each time you refresh the page, or simply navigate away to another page - which you may not want. More logic could be scripted in, that’s for sure). It all depends on what you want to accomplish and how complicated you want it to be.

You can end up doing much more advanced stuff, depending on your HTML and scripting skills. For those willing to experiment there are a lot of useful sites that can help. I would recommend taking a look at dynamicdrive.com for some interesting examples.

For example, here is a more advanced script they have that you could take a look at: