Calcylator isn't a big web 2.0 application, but there are area's where it'll fit quite nicely with some of the new delivery methods.
AJAX is a technology that differentiates traditional websites with 2.0 ones; the basic idea is that pages are delivered to the user with less page refreshes (thus less bandwidth, in turn quicker !). A good example of a 2.0 site vs a traditional one is maps.google.co.uk vs ebay.co.uk. With ebay you'll notice every time you update something the page refreshes & the URL changes. If you look at maps.google you'll notice the URL never changes, in fact if you hit "refresh" on the browser any changes you made to the page disappear.
This all in mind there are area's of calcylator where the page is un-necessarily redrawn; The recently implemented new feature allows you to filter your mini-statement, the filters allow you to view only selling / sold or unsold items, now I could have implemented it traditionally or with ajax. The picture on this post highlights the new tool bar & you'll notice it is massively quick !!!!! To be honest I'm gonna stop there (for now), implementing this ajax code has totally messed up the neatness of what I have written, but I think more ajax could fit in nicely (not too much tho'), but before I put any more in I'm going to make sure the underlying code is ready for it !!!!