Lightbox image appears low on page

[seabird]

1) Script Title:
Lightbox 2.04

2) Script URL (on DD):
http://www.dynamicdrive.com/dynamicindex4/lightbox/index.htm

3) Describe problem:
I struggled for ages with an older version, which I couldn't get to work at all and then found this one - and it works - almost!
BUT the enlarged image appears at the very bottom of the screen, even though the clicked link image is in the centre. Why is this and how can I change it, please? NB there is an iframe on my page - it's a booking calendar. I'm not very techy and I just import that from a third party - surely that shouldn't affect the Lightbox?
ALSO, how do I change the colour of the background to the enlarged image (once I've got it to centre)? I'm sure I read somewhere that you can.
Many thanks in advance.

[seabird]

Continued ...
I should have made it clearer - the image is actually half off the page, not just at the bottom. You have to scroll up to see it.

[bluewalrus]

You should post a link to your page, unless your stating its a bug? Do you see the same thing happen on the demo page that is happening on your page?

[seabird]

No the demo page works fine with images centred. (Presume you mean the tree and the watery scene on the url above).
I have no idea whether it's a bug - I hoped there would be a way to tweak the code to adjust the height. I can't post a link as the page is unfinished and not uploaded yet - although if this is necessary I probably can do it even so. I am very much an amateur at all this and feeling my way.
What sort of fault would cause this to happen?

[jscheuer1]

First things that leap to mind are that you have no valid URL DOCTYPE for the page, and/or - because the script you say you are using is a bit dated, it just isn't up to the task. The latest version is 2.04. The one you linked to in your post is version 1.0.

Anyways, I could be wrong about part or all of this. The only way to really tell would be to have a link to the page so we could be able to snoop around it and see what's what:

Please post a link to the page on your site that contains the problematic code so we can check it out.

Now I know you said the page isn't up anywhere yet. But you also said that it could be if required for us to help you. It is.

[seabird]

Thanks John you are a superstar.
You were right, I had no DOCTYPE, and now I've added one, and the problem is instantly solved!
I am very grateful.
I didn't know about doctypes, so I looked at W3 page on them, added one, and bingo! A friend said she thought Dreamweaver automatically included the doctype but mine didn't - maybe because it's an old version.

I'll ask a separate question about changing the colour in a new thread. Thank you again.
Mary