Mozilla has added the Do Not Track HTTP header discussed last week to the pre-beta build of the upcoming version of Firefox.

The HTTP header is Mozilla's answer to consumer concerns about online behavioral tracking by advertisers.

"If you'd like to try out the feature, grab a nightly build; I must warn you though, these nightlies are not as stable as the beta releases," blogged Mozilla's Sid Stamm. "In the build, to enable the feature, open the preferences pane and select the advanced tab. Tick the box that says "Tell sites I do not want to be tracked" and start browsing."

Every connection the browser makes to download content will send a signal indicating the user does not want to be tracked, Stamm wrote.

"I encourage you to try out the test builds, or if you'd like to wait for a more stable version, wait for an upcoming beta release with the feature in it," he blogged. "We do not anticipate that sites are looking for the signal yet, so you probably won't notice a difference as you browse the web."

Mozilla is not the only browser vendor looking at this issue. Last week, Google announced an extension called 'Keep My Opt-Outs' to address concerns about online tracking, while Microsoft is pushing its Tracking Protection List feature in Internet Explorer 9.