How to make my Multi-Page Photograph Gallery same width as my main 900 pixel width photo at the top?

How to make my Multi-Page Photograph Gallery same width as my main 900 pixel width photo at the top?

https://moskovita-photography.com/

view-source:https://moskovita-photography.com/

ul.download {list-style-image:url(../menus/zip.gif);}
ul.download li {padding-left:5px; font-size:12px; line-height:1.5em;}

/* ================================================================
This copyright notice must be untouched at all times.

The original version of this stylesheet and the associated (x)html
is available at http://www.cssplay.co.uk/menu/lightbox.html
Copyright (c) 2005-2007 Stu Nicholls. All rights reserved.
This stylesheet and the associated (x)html may be modified in any
way to fit your requirements.
=================================================================== */
/* common styling */

a {}
a:hover {}
a:visited {}

/* slides styling */

.photo {width:635px; height:550px; text-align:left; position:relative; margin:0 auto;}

.photo ul.topic {padding:0; margin:0; list-style:none; width:635px; height:auto; position:relative; z-index:10;}

.photo ul.topic li {display:block; width:125px; height:31px; float:left;}
.photo ul.topic li a.set {display:block; font-size:14px; width:124px; height:30px; text-align:center; line-height:30px; color:#000; text-decoration:none; border:1px solid #fff; border-width:1px 1px 0 0; background:#ccc; font-family: 'latolight', verdana, arial, sans-serif; text-transform:uppercase;}

.photo ul.topic li a ul,
.photo ul.topic li ul
{display:none;}

.photo ul.topic li.active a
{color:#000; background:#bbb;}

.photo ul.topic li a:hover,
.photo ul.topic li:hover a
{color:#fff; background:#aaa;}

.photo ul.topic li.active ul
{display:block; position:absolute; left:0; top:31px; list-style:none; padding:0; margin:0; height:375px; background:#ddd; width:464px; padding:40px 60px; border:20px solid #bbb; z-index:1;}

.photo ul.topic li a:hover ul,
.photo ul.topic li:hover ul
{display:block; position:absolute; left:0; top:31px; list-style:none; padding:0; margin:0; height:375px; background:#ddd; width:464px; padding:40px 60px; border:20px solid #aaa; z-index:100;}

.photo ul.topic li ul li
{display:inline; width:112px; height:87px; float:left; border:1px solid #fff; margin:1px;}

.photo ul.topic li ul li a
{display:block; width:110px; height:85px; cursor:default; float:left; text-decoration:none; background:#444; border:1px solid #888;}

.photo ul.topic li ul li a img
{display:block; width:100px; height:75px; border:5px solid #eee;}

.photo ul.topic li a:hover ul li a:hover,
.photo ul.topic li:hover ul li a:hover
{white-space:normal; position:relative;}

.photo ul.topic li a:hover ul li a:hover img,
.photo ul.topic li:hover ul li a:hover img
{position:absolute; left:-50px; top:-32px; width:200px; height:150px; border-color:#fff;}

@media only screen and (max-width:480px) {
.photo {display:none;}
#info h3.smartphone {display:block;}
}

(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
ga('create', 'UA-451410-1', 'auto');
ga('send', 'pageview');