How to add a Font Button in the Top of the Help File

Dear all,

In some of the Help Files (HTML Help), i've seen a Font button being added in the top of the Help File (for e.g next to Home button)...when we click this font button, the font size of the Content present in the Help File Increases/decreases accordingly....how to add this button in our Help File.

At present i'm creating a HTML Help using Adobe 6..Kindly let me know, if there are any options...

Thanks with regards