Welcome to the forum, Sibel.
Tool bar like in the toolbars (Google, Yahoo, AOL) you download for desktop browsers?
You can not do this on the iPad. At lest not in Safari. I believe iCab Mobile can download some tools, (not tool bars though). They will not be the same tools you downloaded on you desktop.
The only place you can get new apps is in the App Store. The only place you can get stuff that modifies the apps you have are with in-app purchases. Some apps have these, and some do not. Safari does not.