On those site asking for your name, address, city, email address, this program would put that info where required. All one had to do was type the first letter or number of the info needed. Is this a Firefox program?
The program would enter info for me. I only had to type the first letter or number of the info needed. For example, my first name is OSCAR. So, to enter this info in the box marked "First name", I only had to type in the box the letter "O". The program would then type OSCAR. I would then click on the name "OSCAR" and the name OSCAR would be entered in the box asking for my first name. Same with "city", "zip code", "last name", "email address", etc. Is this a Firefox feature??
Opaite Mbohovái (1)
That feature would be provided by an add-on for Firefox. The most popular add-on of that type was the Google Toolbar for Firefox, which has been discontinued by Google for Firefox 5 and future versions.
http://googletoolbarhelp.blogspot.com/2011/07/update-on-google-toolbar-for-firefox.html
There are a number of different "auto fill" add-ons that are available from other developers. Look at this search for one that meets your needs.
https://addons.mozilla.org/en-US/firefox/search/?q=auto+fill&cat=all&x=0&y=0