I see a while url has #! combination. What's the reason for that ? &lifier How it's helpful. Can somebody elobrate on that.

Following the hash mark ("#") it's expected the ID of some X/HTML aspect in the page that needs to be outlined or scrolled to through the user agent. Valid HTML ID characteristics cannot contain "!", therefore it seems guaranteed that whatever follows "#" here won't match any aspect in the page.

This trick is once had a variety of Web addresses towards the same page, and let a javascript within the page alter it by interpretation what uses "#", possibly via AJAX. It has faster load occasions than when the user needed to visit different pages. Also, it's bookmark and back button friendly.

If you notice #! realize that this website is applying Ajax. Whenever you click a hyperlink it does not refresh whole page.

So why do they will use #! ? Next sign installed the road from the page. If you work with old version of browser that does not support Ajax well, the script opens the page without Ajax.

http://code.google.com/web/ajaxcrawling/paperwork/getting-began.html

It's essentially conforming to Google's ajax url standard. There's no miracle behind it, but google wants sites to possess consistent url designs for ajax-powered sites.