I am not sure what your working environment is. I do not have right to install software in my office computer and my office does not encourage web surfing for private use. I highly recommend the following software for safer web surfing in office:
1. Portable Firefox
A portable software means that it can be installed without administrative right. I recommend Firefox because it is a fast web browser that allows you to visit website and close your browser faster. Firefox has a setting that clean up your history and temporary Internet files when closing the browser. The most important function is that Firefox has many addons that make you visit websites safer in office.
2. Firefox extension - Page Title Eraser
As what you may understand from the name of the addons, Page Title Eraser allows you to hide title and icon of the selected tab by using hot key (Ctrl + Alt + Shift + H) or from "Right-click" menu. So when you boss comes behind you. You could simply minimize your web browser without closing it.
3. Firefox extension - Panic
This extension allows you to close all tabs and opening another one that you want to show your boss. When your boss goes away, you could restore to the website that you browse before.
4. Firefox extension - Adblock Plus
Adblock allows you to block the Flash content on screen. As Flash content is more visible far-way than words and advertisement is useless, this extension make you free of the danger from useless advertisement.
My last recommendation is not to visit website in workplace too often. The software above could not delete the browsing history in office sever. When the boss checks for the browsing history, everything would be known. The softwares above is just use for occasional use.