Causes For The Loading Icon

[ghostshell]

What are the reasons/common causes for seeing the loading circle on the web gui? Sometimes i never see it, sometimes i see for a while as it loads the firewall rules page, also it will show up when loading the firewall rules page but just for a moment. I may see it on other pages, but last night i was mainly in the firewall rules page working on my rule set.

2.1.3 i386 Full Install