"Technology that supports something like a 'Do Not Track' button is needed and we will deliver in the first part of next year," Mozilla chief executive Gary Kovacs said while providing a glimpse at Firefox 4 at the Mozilla's headquarters in Mountain View, California. "The user needs to be in control," he added. There is a disturbing imbalance between what websites need to know about visitors to personalize advertisements or services and the amount of data collected, according to Kovacs.