I view my blog alexa rank often. The rank changes daily. It meants alexa has a great statistic update daily, show in picture below.
Biside that alexa also have site widgets and toolar to help us view Alexa rank directly. Thanks for Alexa internet.
Toolbar [For Mozila Firefox]
Do you see..?? The Rank is different.. I capture the image in one time.. The newest update of alexa rank is in the Alexa Web, not in site widget or toolbar.