It depends on your settings, if you want the "A" ball to spin (scan your programs on open) left click the avast "A" ball (next to your system clock) and it will bring up a bix, select "standard Shield" from the left side and then slid the bar over to "High" in the top right hand corner, then when you open a program, the avast ball should spin.
But the Avast ball should spin if your just switching between URLs (webpages) on the internet.
--lee