一个web网站的界面修改问题

遇到一个项目。 用到javascript做的网站。 我要修改其中一个页面。可俺是新手。不懂做网站。希望高手指点下。
下面是他主页的代码
<html>
    <head>
        <title></title>
        <meta http-equiv='Content-Type' content='text/html; charset=utf-8' />
        <style type='text/css'>
            /*margin and padding on body element
            can introduce errors in determining
            element position and are not recommended;
            we turn them off as a foundation for YUI
            CSS treatments. */
            body {
                margin:0;
                padding:0;
                height:100%;
            }
        </style>        <link rel='stylesheet' type='text/css' href='Client/build/fonts/fonts-min.css' />
        <link rel='stylesheet' type='text/css' href='Client/build/button/assets/skins/sam/button.css'/>
        <link rel='stylesheet' type='text/css' href='Client/build/container/assets/skins/sam/container.css'/>
        <link rel="stylesheet" type="text/css" href="Client/build/treeview/assets/skins/sam/treeview.css" />
        <link rel="stylesheet" type="text/css" href="Client/build/menu/assets/skins/sam/menu.css"/> 
        <link rel="stylesheet" type="text/css" href="Client/build/logger/assets/skins/sam/logger.css"/>
        <link rel="stylesheet" type="text/css" href="Client/build/calendar/assets/skins/sam/calendar.css"/>
        <script type='text/javascript' src='Client/prototype.js'></script>
        <script type='text/javascript' src='Client/soapclient.js'></script>
        <link rel='stylesheet' type='text/css' href='Client/css/style.css'/>        <script type='text/javascript' src='Client/build/yahoo-dom-event/yahoo-dom-event.js'></script>
        <script type='text/javascript' src='Client/build/element/element-beta.js'></script>
        <script type='text/javascript' src='Client/build/utilities/utilities.js'></script>
        <script type='text/javascript' src='Client/build/button/button-beta.js'></script>
        <script type='text/javascript' src='Client/build/container/container.js'></script>
        <script type='text/javascript' src='Client/build/dragdrop/dragdrop.js'></script>
        <script type="text/javascript" src="Client/build/yahoo/yahoo.js"></script>
        <script type="text/javascript" src="Client/build/event/event.js"></script>
        <script type="text/javascript" src="Client/build/treeview/treeview.js"></script>
        <script type="text/javascript" src="Client/build/dom/dom.js"></script>
        <script type="text/javascript" src="Client/build/animation/animation.js"></script>
        <script type="text/javascript" src="Client/build/container/container_core.js"></script>
        <script type="text/javascript" src="Client/build/menu/menu.js"></script>
        <script type="text/javascript" src="Client/build/logger/logger-min.js"></script>
        <script type="text/javascript" src="Client/build/dragdrop/dragdrop.js"></script>
        <script type="text/javascript" src="Client/build/calendar/calendar.js"></script>
        <script type="text/javascript">
        
        //摄像机树
        var globalTree;
        YAHOO_config = 
        {
            load: 
            {
                require: ['animation', 'fonts', 'button', 'element', 'dragdrop','logger', 'container', 'dom', 'event', 'menu', 'treeview', 'yahoo'],
                base: 'build/'
                //filter: 'DEBUG'
            }
        };
   
        </script>
        <script type="text/javascript" src="Client/build/yuiloader/yuiloader-beta.js"></script>
        <!--
        NOTE : Every javascript source file name should contain only lowercase letter.
        -->
        <script type='text/javascript' src='Client/js/namespace.js'></script>
        <script type='text/javascript' src='Client/js/cookie.js'></script>
        <script type='text/javascript' src='Client/js/soap.js'></script>
        <script type='text/javascript' src='Client/js/resources.en.js'></script>
        <script type='text/javascript' src='Client/js/resources.zh.js'></script>
        <script type='text/javascript' src='Client/js/cleanup.js'></script>
        <script type='text/javascript' src='Client/js/logon.js'></script>
        <script type='text/javascript' src='Client/js/setup.js'></script>
        <script type='text/javascript' src='Client/js/dialog.js'></script>
        <script type='text/javascript' src='Client/js/ui.js'></script>
        <script type='text/javascript' src='Client/js/common.js'></script>        
    </head>
    <body class='yui-skin-sam' onload="VCAnywhere.LogOn.loadRefresh()" onbeforeunload="VCAnywhere.UI.IeCloseLogOutSystem()" onselectstart = "return event.srcElement.tagName == 'INPUT'">
        <div id='statusBlock'>
            <noscript>Javascript is not available!</noscript>
        </div>
        <div id='logonDialog' style='display : none'>
            <div class='hd'><script>document.write(VCAnywhere.Resources.zh.H3C_IVS_WEB);</script></div>
            <div class='bd'>
                <table cellspacing="5" cellpadding="5" border="0">
                <tr>
                    <td width="55%"><IMG width="300" height="200" SRC="Client/a_logo_login_3.gif" /></td>
                    <td>
                    <table width="100%">
                    <form id='logon_form'>
                    <tr><td><label for='userName'><script>document.write(VCAnywhere.Resources.zh.userName);</script></label></td></tr>
                    <tr><td><input type='textbox' name='userName'id = 'userName' maxlength='15'onKeyPress=check_userName(this) class='logonInput'"/><br /></td></tr>
                    <tr><td><label for='password'><script>document.write(VCAnywhere.Resources.zh.PassWord);</script></label></td></tr>
                    <tr><td><input type='password' name='password' id = 'password' maxlength='15' onKeyPress=check_passwd(this) class='logonInput'/><br /></td></tr>
                    <!--<tr><td><label for='serverIP'>服务器地址：</label><input type='textbox' name='serverIP' class='logonInput'/></td></tr>-->
                    <tr><td><label for='clientIP'><script>document.write(VCAnywhere.Resources.zh.localIP);</script></label></td></tr>
                    <tr><td><input type='textbox' name='clientIP'id = 'clientIP' maxlength='20' onKeyPress=check_clientIP(this) class='logonInput' /> </td></tr>
                    <tr><td><div class='clear' nowrap>&nbsp;</div>
                        <label for='saveLogonInfo' class='check'><script>document.write(VCAnywhere.Resources.zh.saveLogonInfo);</script></label><input type='checkbox'id = 'saveLogonInfo' name='saveLogonInfo' checked='true'/>
                        <div class='clear'></div>
                    </td></tr>                    
                    </form>                    
                    </table>
                    </td>
                </tr>
                </table>
            </div>
        </div>
        <div>
            <input id="selectFile" type="file" onchange="VCAnywhere.UI.DealPlayLocalRecord(this)" style="visibility:hidden">
        </div>
        <div id='logger'/>
    </body>
    
    <script language="JavaScript" for="mp" event="NotifyMainWnd(lChannelIndex, eventType)">
        VCAnywhere.LogOn.MpEventCallBack(lChannelIndex, eventType);
    </script>
</html>
里面写的那些.js结尾的就是和界面相关的一些东西。
我不明白：
1）这个主页 如何调用这些js并形成界面的？这类技术的网站是怎么个工作流程？（比如先执行那个函数，然后在客户端还是服务器端运行代码等等）
2） 如果我要修改上边文本里那个叫ui.js 。比如+个log  该如何修改？
3） 为什么.js文件里的东西不能直接用dw或者.net这样的编辑器来可视化的编辑？
如果需要别的代码可以加我
我的qq号：61030398
谢谢啦