They are two way that i now . The First way is

By default, Mozilla Firefox and Google Chrome Web browsers all store a few pieces of information about the websites you visit and interact with. In addition to logging the time, date, title and URL of every page you view, each browser also stores the data you enter into search boxes or other form fields. Although this feature is intended to help you access information more quickly, it also exposes your usage history to anyone with access to your computer. Deleting these autofill entries requires just a few clicks.
Instructions:- Mozilla Firefox
Click "Tools" in the top menu bar and select "Clear Recent History."
Click the "Time range to clear" drop-down menu near the top of the resulting window and select "Everything."
Click the adjacent "Details" button to view Firefox's history removal options.
Check only the "Form & Search History" box.
Click the "Clear Now" button.
Instructions:- Google Chrome
Click the wrench icon near the top-right corner of the window, select "Tools," then click "Clear browsing data."
Check only the "Clear saved form data" box in the resulting window.
Click the "Clear data from this period" drop-down menu and select "Everything."
Click the "Clear browsing data" button.
The secound way is :-Install Sweeper and KleanSweep
Sweeper (System Cleaner)
What is Sweeper :-Sweeper can quickly remove temporary information, such as web page cookies, browser history, or the list of recently-opened documents. It helps provide additional privacy on a system shared between multiple users.

how to install go to Applications --> Ubuntu Software Center ---> and type sweeper in surch box

After installing you wnat to go sweeper go to applications --> Accessories --> Sweeper

and you can quickly do the job which you want






Klean Sweep (Find and remove unneeded files)

what is Klean Sweep:-Sweeper can quickly remove temporary information, such as web page cookies, browser history, or the list of recently-opened documents. It helps provide additional privacy on a system shared between multiple users.
1.empty files 2. empty directories 3.backup files 4. broken symbolic links 5. broken executables (executables with missing libraries) 6. dead menu entries (.desktop files pointing to non-existing executables) 7. duplicated files 8. orphaned files -- files not found in RPM (for rpm-based distros, e.g.
Fedora Core, Suse) or DPKG (for dpkg based distros, e.g. Debian and Ubuntu) database - obsolete thumbnails (thumbnails conforming to freedesktop.org standard, pointing to non-existing images)

how to install Klean Sweep in ubuntu:- first you have to go Applications --> Ubuntu Software Center ---> and type Klean Sweep in surch box

after installation is over you want to open klean sweep you have to go Applications --> System Tools --> KleanSweep

after press on KleanSweep it will ask you system password you have to give

after giveing password it will open with two windows one is Information-KleanSweep

in that you will see this information

“You are running KleanSweep with root privileges. Therefore
extreme caution is recommended as improper use may render
your system unusable. Please keep in mind that because KleanSweep
uses simple heuristics, all files suggested for removal should be
manually reviewed.”

if you want to run KelanSweep press OK button

and now you have to read on secound box information that is KleanSweep (Welcom!)

that infromation is like this

“Welcome to KleanSweep! This application allows you to free some desk sapce by finding unneeded files on your system. you”ll be given a chance to backup and remove selected files and reclaim your disk space!

Beware! This utility is menat for advanced users only. It is assumed that you have some basic understanding of what can be safely deleted. The author takes no responsibility for any damage caused by using this program”

Note:- so you have to very carefull when you are using Klean Sweep if you have very good grip in ubuntu than only you use this Klean Sweep softer.

Allu John Sudhakar
System/Network Administrator
UCE,OU Osmania University
Hyderbad

There's also an application called "bleachbit".