Aligning html page content to center of screen

I have a html page whose content is  not aligning up in the center of the screen. See image below - it is aligned to the left.  I have a css approach but that does not work for me. The page code, including the css is attached below.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "xhtml11.dtd">
<html>
<head>

<style type="text/css">
                html
                {
                    width: 100%;
                    height: 100%;
                }

                body
                {
                    display: flex;
                    justify-content: center;
                    align-items: center;
                }
            </style>


<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

<title>Highslide JS - Custom Example</title>

<script type="text/javascript" src="highslide/highslide-with-gallery.js"></script>
<script type="text/javascript" src="highslide/highslide.config.js" charset="utf-8"></script>
<link rel="stylesheet" type="text/css" href="highslide/highslide.css" />

</head>


<body>
<div class="highslide-gallery">
	<ul>
	<li>
	<a href="highslide/images/large/IMG_8198_reworked.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_8198_reworked.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/IMG_3632.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_3632.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy23.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy23.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy14.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy14.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy22.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy22.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy18.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy18.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy13.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy13.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/IMG_3617.jpg" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_3617.jpg"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy20.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy20.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy15.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy15.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/business_card.jpg" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/business_card.jpg"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/IMG_4290.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_4290.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image2.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image2.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/IMG_3632_reworked.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_3632_reworked.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy19.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy19.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/IMG_8198.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_8198.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy12.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy12.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy16.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy16.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy21.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy21.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image3.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image3.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/IMG_4290_reworked.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_4290_reworked.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	<li>
	<a href="highslide/images/large/image_1-Copy17.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/image_1-Copy17.png"  alt=""
			title="Heading from the thumbnail's title attribute" />
	</a>
	</li>
	</ul>
	<div style="clear:both"></div></div>

</body>


</html>

</div>

Open in new window

.

I do not have much css experience, so that must exxplain it.

 Thanks for taking a look

James


Image of screen with highslide editor content
jameskaneAsked:
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myderrickCommented:
Hi James,

Add
margin: 0 auto

Open in new window

to the main div (class) wrapping the content you want to center. That is the highslide-gallery.

Good luck.

MD
jameskaneAuthor Commented:
Many thanks for reply.  I have made the change (I think) you suggested -but it is not aligning.

Attach the code segment I changed.

James
<body>
<div class="highslide-gallery" margin: 0 auto>
	<ul>
	<li>
	<a href="highslide/images/large/IMG_8198_reworked.png" class="highslide" 
			title="" 
			onclick="return hs.expand(this, config1 )">
		<img src="highslide/images/thumbs/IMG_8198_reworked.png"  alt=""
			title="Heading from the thumbnail's title attribu

Open in new window

myderrickCommented:
Hi James,

I meant that you should add it in your CSS file highslide.css.

Locate the class .highslide-gallery and add the margin: 0 auto.

Alternatively you can send a copy of the highslide CDs.

Thanks.

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jameskaneAuthor Commented:
That works,  many thanks for your help and patience !
myderrickCommented:
Glad it did. Have a nice weekend.

MD
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