//All you have to do is to add files to this list below:
//First get your list of files in the order you want them:
database=new Array(
"index.htm"
);
//The above is all you need to change!
//We want to automatically discover the number of files
NumberOfFiles=database.length;
//Next find out which page, this one is//
//We use the location.href property and extract the filename
//from this string using lastIndexOf:
StringA=location.href;
LengthA=StringA.length
A=StringA.lastIndexOf("/")+1;
ThisFilename=StringA.substring(A,LengthA);

//Now we find the current page nunmber (in the list)
//Remember that Arrays start at 0 and end at number of 
//elements less one. So the last element is:
n=NumberOfFiles-1;
//Now we look through to list to find our file, and 
//therefore, its number in the list:
for (var i = 0; i <= n; i++)
{
if (database[i]==ThisFilename)
{
ThisPageNumber=i;
}
}
//determine the numbers of the previous and the next pages//
function goBack(){
if (ThisPageNumber-1<0)
//We don't want to go into negative numbers or numbers
//bigger than the number of files! So if the file number less
//one is less than zero, there is nowhere left to go!
{
alert("To jest pierwsza strona")
}
//Otherwise we just take one of the current file number
//and get the number for the previous file:
else
{top.location=database[ThisPageNumber-1]}}
function goForward(){
if (ThisPageNumber+1>n){
alert("To już jest ostatnia strona")
//If the user is clicking on the last file, he or she
//cannot go forward. Otherwise, the next file is the current
//file number plus one:
}
else
{top.location=database[ThisPageNumber+1]}}

//and so that's our code. All we have to do is to change files
//in the Array database! Nice and lazy!