The pop-up window provides a short list of the improvements in the latest version of the browser and offers users the option of updating immediately, sending another reminder later, or never asking the user to update again.
Because Firefox lacks the type of automatic standalone update utility employed by Apple and Microsoft for updating Safari and Internet Explorer, Mozilla relies on alert messages within the browser to update users when a new version of Firefox is available.
The new components of the browser, most notably the built-in antimalware tools, require the company to issue a new end-user license agreement, unlike most Firefox updates.
The user will also be presented with an additional dialog box if any plug-ins are found to be incompatible with the new browser.
Mozilla estimates that roughly 10 per cent of all Firefox 2 plug-ins are incompatible with version 3, though the company notes that developers have released new versions of many of the incompatible tools.
The move will push Firefox 3 from an update for early adopters to the current standard version of the browser.
Microsoft made a similar declaration with Internet Explorer 7 in February when the browser was pushed to users through the automated Windows update services.
Mozilla launched Firefox 3 to great fanfare earlier this year. The browser was released amidst a marketing push from Mozilla that included a Guinness World Record attempt.
When it was all said and done, Firefox 3 logged 8.2 million downloads in its first 24 hours, and more than 25 million within two weeks.