Beautiful! I substituted my own bj.jpg and button.png, everything worked fine.
BTW, when I saved the css (via the style editor) I saved it as "style-1.css" and that worked fine, then as a test I changed that name to "style1.css" it still worked, so I guess I just got lucky . . so then I changed it to "style-whatever" and it still worked, so . . ignorance is definitely bliss
Then I had fun fiddling around with the html and css . . I'm such an amateur at this stuff I hadn't known that style.css code could be put in index.html, my fiddling got me nowhere but at least familiarized me a bit with how that can be done. Is there a reason for putting the styling code in html instead of a style.css file?
What I'll do now is try to re-create your code in my own modal, but I'm sure that's going to require some time, plus Thanksgiving's coming up so I'll be away from the infernal machine for 5 or 6 days, so you might not hear back from me for a while
If you want to have a look at the modal window I'm trying to put the button in, click the "Help!" button at the prototype site. The Reddit button you'll see is just photoshopped in, it's where I'm hoping to be able to put in a real button link.
Tom, you are so kind . . and patient! . . . most people would have given up on me long ago