Not too while ago, writing a web application meant you compromised yourself with all “the goods and bads” of a web environment. The same goes when writing a desktop application. The gap was quite obvious (it still is...).
Nowadays, WPF and Silverlight have narrowed that gap and the similarities between a web application and a desktop application are increasing. But writing a desktop application using WPF doesn’t mean you have a Silverlight web application. Despite the fact that “both are XAML based platforms, there are some important functionality and implementation differences between the two”. Having this in mind, Microsoft has asked Wintellect to write a white paper about the differences between these two technologies.
It’s interesting, here is the link: http://wpfslguidance.codeplex.com
And here’s the Wintellect post on this issue: John Robbins@Wintellect