[ruslan_mart]

var url = location.href;

if(url == 'http://site.com/page/1') document.write('This is page №1');
else if(url == 'http://site.com/page/2') document.write('This is page №2');
else if(url == 'http://site.com/page/3') document.write('This is page №3');

Но ещё лучше, сделать через объект:

var urls = {
   'http://site.com/page/1' : 'This is page №1',
   'http://site.com/page/2' : 'This is page №2',
   'http://site.com/page/3' : 'This is page №3'
}

document.write(urls[location.href]);