How can I browse with localstorage disabled?

For Firefox:

Dom.storage.enabled

The Web Applications 1.0 specification defines a mechanism allowing web pages to store information with a web browser (similar to cookies) called “client-side session and persistent storage.” Although use of session storage is subject to a user’s cookie preferences, this preference allows it to be disabled entirely.

For Chrome:

Chrome/Chromium – disable HTML5 LocalStorage and Databases for all webpages /or ask user

While some resources on the Internet claims that Chrome’s cookie blocking does not also block LocalStorage, I just ran a quick test and discovered that it does actually block LocalStorage, (at least in Chrome 12, the current beta version).

For IE:

Internet Explorer

Select “Tools” -> “Internet Options” -> “General” -> check “Delete browsing history on exit”, click on “Delete”, check “Cookies”, click on “Delete” once more and restart your browser afterwards.

Not really sure about Safari but I imagine it is similar to Chrome.