If you’re a ASP.NET (WebForm) web developer and you worry about Viewstate (which you should!) – you might find this Firefox add-on very useful:
https://addons.mozilla.org/en-US/firefox/addon/aspnet-viewstate-viewer/?src=api
The add-on displays the viewstate of the current ASP.NET page in the statusbar – very handy when trying to limit the Viewstate size.