Many websites contain active content such as JavaScript, Flash, and HTML5 to
provide a rich and dynamic web-browsing experience. Unfortunately, these
web applicationsmayalso contain software bugs, which can result in sluggish
response times and can even cause the web browser to crash. This isn’t a big
problem in a web browser that displays content from only one website. But
most contemporary web browsers provide tabbed browsing, which allows a
single instance of a web browser application to open several websites at the
same time, with each site in a separate tab. To switch between the different
sites , a user need only click on the appropriate tab. This arrangement is
illustrated below: