Today i am going to introduce a mozilla add on which will very helpful for web developers (for hackers also).
Features:
View/Add/Edit Cookies
Clear cookies
Disable image in website
Disable java script in website
Disable css in website
more…
Download and install the add on from here:
https://addons.mozilla.org/en-US/firefox/addon/60
or try this
https://addons.mozilla.org/en-US/firefox/addon/web-developer/