How to reduce tab spacing in this javascript?

I have hacked this tab system together.

I need to reduce the spacing(padding) between each tab. When viewed in firebug, you can see the javascript function is adding various left pixels between each, but instead of random padding-left pixels I need padding-left: 100px between each tab. Any idea how I can do that?

Below is the javascript.

<script type="text/javascript">
var menuAlignment = 'left'; // Align menu to the left or right?     
var topMenuSpacer = 0; // Horizontal space(pixels) between the main menu items  
var activateSubOnClick = false; // if true-> Show sub menu items on click, if false, show submenu items onmouseover
var leftAlignSubItems = true;   // left align sub items t

var activeMenuItem = false; // Don't change this option. It should initially be false
var activeTabIndex = 0; // Index of initial active tab  (0 = first tab) - If the value below is set to true, it will override this one.
var rememberActiveTabByCookie = true;   // Set it to true if you want to be able to save active tab as cookie

var MSIE = navigator.userAgent.indexOf('MSIE')>=0?true:false;
var Opera = navigator.userAgent.indexOf('Opera')>=0?true:false;
var navigatorVersion = navigator.appVersion.replace(/.*?MSIE ([0-9]\.[0-9]).*/g,'$1')/1;

/*
These cookie functions are downloaded from 
http://www.mach5.com/support/analyzer/manual/html/General/CookiesJavaScript.htm
*/  
function Get_Cookie(name) { 
   var start = document.cookie.indexOf(name+"="); 
   var len = start+name.length+1; 
   if ((!start) && (name != document.cookie.substring(0,name.length))) return null; 
   if (start == -1) return null; 
   var end = document.cookie.indexOf(";",len); 
   if (end == -1) end = document.cookie.length; 
   return unescape(document.cookie.substring(len,end)); 
} 
// This function has been slightly modified
function Set_Cookie(name,value,expires,path,domain,secure) { 
    expires = expires * 60*60*24*1000;
    var today = new Date();
    var expires_date = new Date( today.getTime() + (expires) );
    var cookieString = name + "=" +escape(value) + 
       ( (expires) ? ";expires=" + expires_date.toGMTString() : "") + 
       ( (path) ? ";path=" + path : "") + 
       ( (domain) ? ";domain=" + domain : "") + 
       ( (secure) ? ";secure" : ""); 
    document.cookie = cookieString; 
}   

function showHide()
{
    if(activeMenuItem){
        activeMenuItem.className = 'inactiveMenuItem';  
        var theId = activeMenuItem.id.replace(/[^0-9]/g,'');
        document.getElementById('submenu_'+theId).style.display='none';
        var img = activeMenuItem.getElementsByTagName('IMG');
        if(img.length>0)img[0].style.display='none';            
    }

    var img = this.getElementsByTagName('IMG');
    if(img.length>0)img[0].style.display='inline';

    activeMenuItem = this;      
    this.className = 'activeMenuItem';
    var theId = this.id.replace(/[^0-9]/g,'');
    document.getElementById('submenu_'+theId).style.display='block';



    if(rememberActiveTabByCookie){
        Set_Cookie('dhtmlgoodies_tab_menu_tabIndex','index: ' + (theId-1),100);
    }
}

function initMenu()
{
    var mainMenuObj = document.getElementById('mainMenu');
    var menuItems = mainMenuObj.getElementsByTagName('A');
    if(document.all){
        mainMenuObj.style.visibility = 'hidden';
        document.getElementById('submenu').style.visibility='hidden';
    }       
    if(rememberActiveTabByCookie){
        var cookieValue = Get_Cookie('dhtmlgoodies_tab_menu_tabIndex') + '';
        cookieValue = cookieValue.replace(/[^0-9]/g,'');
        if(cookieValue.length>0 && cookieValue<menuItems.length){
            activeTabIndex = cookieValue/1;
        }           
    }

    var currentLeftPos = 1;
    for(var no=0;no<menuItems.length;no++){         
        if(activateSubOnClick)menuItems[no].onclick = showHide; else menuItems[no].onmouseover = showHide;
        menuItems[no].id = 'mainMenuItem' + (no+1);
        if(menuAlignment=='left')
            menuItems[no].style.left = currentLeftPos + 'px';
        else
            menuItems[no].style.right = currentLeftPos + 'px';
        currentLeftPos = currentLeftPos + menuItems[no].offsetWidth + topMenuSpacer; 

        var img = menuItems[no].getElementsByTagName('IMG');
        if(img.length>0){
            img[0].style.display='none';
            if(MSIE && !Opera && navigatorVersion<7){
                img[0].style.bottom = '-1px';
                img[0].style.right = '-1px';
            }
        }

        if(no==activeTabIndex){
            menuItems[no].className='activeMenuItem';
            activeMenuItem = menuItems[no];
            var img = activeMenuItem.getElementsByTagName('IMG');
            if(img.length>0)img[0].style.display='inline';  

        }else menuItems[no].className='inactiveMenuItem';
        if(!document.all)menuItems[no].style.bottom = '-1px';
        if(MSIE && navigatorVersion < 6)menuItems[no].style.bottom = '-2px';


    }       

    var mainMenuLinks = mainMenuObj.getElementsByTagName('A');

    var subCounter = 1;
    var parentWidth = mainMenuObj.offsetWidth;
    while(document.getElementById('submenu_' + subCounter)){
        var subItem = document.getElementById('submenu_' + subCounter);

        if(leftAlignSubItems){
            // No action
        }else{                          
            var leftPos = mainMenuLinks[subCounter-1].offsetLeft;
            document.getElementById('submenu_'+subCounter).style.paddingLeft =  LeftPos + 'px';
            subItem.style.position ='absolute';
            if(subItem.offsetWid开发者_Go百科th > parentWidth){
                leftPos = leftPos - Math.max(0,subItem.offsetWidth-parentWidth);    
            }
            subItem.style.paddingLeft =  leftPos + 'px';
            subItem.style.position ='static';


        }
        if(subCounter==(activeTabIndex+1)){
            subItem.style.display='block';
        }else{
            subItem.style.display='none';
        }

        subCounter++;
    }
    if(document.all){
        mainMenuObj.style.visibility = 'visible';
        document.getElementById('submenu').style.visibility='visible';
    }       
    document.getElementById('submenu').style.display='block';
}
window.onload = initMenu;   
</script>

I don't want to put down your effort, but your solution looks very complicated, feels slow on a 3Ghz dual-core workstation, throws a lot of Javascript errors and, as your question illustrates, makes customization very difficult. I'm not sure this is the way to go - I find it hard to dig into the script to even find the place to make the change you want to make.

Why not, for example, use something pre-built and small like the old but mostly reliable framework-agnostic DOMTab? There is a great number of tab scripts based on the popular frameworks as well, see e.g. here.