I use Photoshop -- in Photoshop there are several ways to make the pixel transparent -- including the gif89a export, which lets you choose transparency by color. So you can start with a white pixel and then choose white as the transparent color. Whatever image editor you are using, check the help files for how to create GIF transparency.
Yes, you can just upload clearpixel.gif to the same folder as the HTML document on your server.
I'm missing your point on hiding the gif file, however. First, I never heard of a way to do this, and second, I don't understand why it is a problem. Can you fill us in a little more?
Thanks, I understand how to make it now, I took a look at Photoshop. I don't use it much. It isn't really a problem, it's this:
I'm looking at a competitor's excellent pages and when I try to go to www.herpages.com/clearpixel.gif I go to her homepage. If I try to go to www.herpages.com/anypage/ I go to her home page. In other words if I try to go to any page other than her home page or one of her named pages, or her site with a page name I make up, I end up at her homepage. When I try that on my site, I get the message: "Page not found." I wondered how she did this.