Spoofing is the act of configuring your web access program, your browser or Hana, so that web sites or web apps are led to believe your application is actually another application.
Simply put: faking out the web app so that it thinks Hana is a web browser such as Safari or Firefox.
Why is this necessary? Microsoft, Apple, Mozilla and the other browser developers all implement the key technologies of the web a little bit differently. Ideally, all would implement the web standards the same. But they don't. So web app vendors have to write their HTML/XHTML/XML (the "data code" of the page) just *so* to work in this browser and just *so* to work in that browser and just *so* to work in both. The same goes for Javascript (the "programming code" a.k.a. client side code of the page) and the CSS, (the styling code.) The various web app publishers have to pick and choose what to support and often times support for Webkit based applications fall out of the picture.
Since many web apps that restrict access based on user agent string are doing so out of a desire to simply not have to think about supporting Safari, they just lock out Safari and deal with Internet Explorer and Firefox. But in many cases, Safari works just fine, even if it may be a little odd looking and quirky. Hana gives you the ability to try to access these web apps without having to download another browser or even to have to use a browser. Hana is best for web apps!
Spoofing carries some risk. Use it sparingly and save your work often.