wait a minute,
where does your forum or blog get the traffic from??

google likes so called "Clean" traffic,
it would be better to check your adsense account,

under the "site diagnostics" tab,
see if theres any problem,

and if the traffic is from referring sites with high pr,
than you'll get good money,

but if it's bad traffic,
you'd get a slightly lower cpc value,

well,
thats only one the factors,

i guess you need more professional advice....

Oh, well my traffic came from all types of advertising (excluding email spam)..

Most of them came from forum advertising and SEO friendly directories and article sites..

Checking the diagnostic, I don't have any blocked URL...

i've learn the hard way,
that google prefers,

traffic from article site,
compared to directory sites,

unless the directory sites have high pr,
and you know it's hard to get listed free in high pr sites~

hope your listed in dmoz

Well it's a hard thing to get listed in DEMOZ nowadays...anyway, another adsense expert told me that regardless of the high paying keywords, I can get lower CPC if the clickers/visitors came from Asian, Africam South American, or other European countries...

and seems he is right about this.... I advertised my site in a Brazilian forum where I got around 14 clicks yesterday and the result was very poor..LOL. I learned another lesson from that activity... I was not aware that could affect my CPC..

WOW thanks for the info,
i guess i better start listing my site on U.S. directories,

well might as well write a few articles,
then just post them on ezines-article.com~ HA

Its all due to the google advt keywords which your site got that day , some have high and some have low.

Yeah, I know how to use competitive ad filter but the big question is, how do we know find out these low cpc sites?

How could we identify if the site in adsense is MFA or not?

If you use adlogger (http://adlogger.org) you can see all your clicks on which advertiser were made, and you can see if this site is MFA or not.

Or simply look at ads on your site, write the site address, open it in new window and see the site. (remember not to click on ads on your site)

might as well use an adsense preview tool,
firefox has it,
ie has it,

or you can open ie tab in firefox and use ie adsense preview tool~
copy the link and update it on your filter

I think using adlogger is a good idea.... Thanks