@Suramya.K , do you understand what is CPM advertising?
At the beginning i also had a CPM rate over 5 dollar but yesterday i was shocked to see .15 cents for per 100 page views.
I guess it's because , Premium advertiser gives a certain amount of money to Hubpages for isplaying their ads per month. For example if the advertiser spend 10,000 dollars in 1 month and the total view is 1000000 then the CPM rate for per 1000 is 10 dollars. Now as hubpages showing the ad more frequently everywhere the amount page views is increasing and the CPM rate is decreasing. Now if for that 10,000 dollar budget if the advertiser gets 10000000 views then the CPM rate will be 1 dollar only.