Types of web widgets

There are three basic types of web widgets - javascript, iframe and flash. Each has pros and cons.

1. Javascript. <script ../>

Fetched via XHTTP script request, return JSON. Widget is inserted by direct manipulation of the HTML document (DOM). Pros: Allows dynamic sizing and multi-threading, and static monitoring. Possible issues with cross-site scripting. Cons: Uses complex technologies (JavaScript, DOM, JSON/XML, DOJO/pototype/jQuery/DWR/...). Allowed by most (but not all) third party sites.

2. IFrame. <iframe ... />

Fetched via HTTPRequest, returns HTML. Widget is inserted into fixed-size window on parent document. Widget is just another HTML page. Pros: Uses simple technologies, cross-site scripting is fine. Cons: fixed size, tricky communicating between documents, distribution difficult

3. Flash. <embed ... />

Fetched via HHTP resource request, returns WF/binary file. Pros: powerful graphics, run on sites that don't allow JavaScript (eg. MySpace). Cons: expensive tools, trickier to tweak.