How do I make something stay put as I scroll down the page?

Use css. Create a class using fixed positioning and the top/left/bottom/right properties to place it where you want it...

.your_image {

position:fixed;

top:0;

left:0;

}

Then add that class to the image in your html...

<img src="image.jpg" class="your_image" alt="some text">

The above will stick your image to the top left corner of the browser window and it will float over the top of everything else on the page when you scroll. Doing this takes the image entirely out of the normal flow of your document, so it will likely overlap content if you don't specifically design the remainder of page around that fact.