Today my blog suddenly receive less traffic from Google search, and when i check my blog on Google Search using keyword that usually show my blog on top ten result, suddenly disappointed me. I don't know what happen today but yesterday my blog traffic is just Okay.
Does anyone have the same problem with me??
Anyone have information about what happen??

It's possible you got hit with a penalty.

Are you selling links?

Did anything change in your hosting recently?

Have you made any changes to your theme? (internal linking structure?)

An alternative answer is that there is an influx of competitors for your keyword and they are simply ranking a lot higher than you.

No, I'm not selling any links, but yes i was registered my self to TLA but didn't include the script into my blog.
I think you're right with the last one, may be what i need to do is get more backlinks and do more promotion.
Btw, thanks for your reply.

I started see some older sites yesterday drop out of the top rankings and then back to the top within the same day, so this could be one of those reindexing issues.

If you are currently undertaking search engine optimisation steps to promote your website then please do not take any drastic actions just yet of the fall in rank is not very significant. Sometimes as a result of SEO work ranking may get affected negatively for a short time and then rise again. I would suggest that wait and watch before changing your strategy.

google SERP is moving fast this days, one week ago for certain keywords my website was in second page, yesterday was in 7. page and today in first page

Yes, right,
Some one told me that this all because of something like Google dance, SERP dropped on that day and back to normal again now.

Just to add to my previous reply. Our website had fallen for the keyword 'Web design company' on Google UK from page 4 to page 10 after 6 weeks of intensive search engine optimisation work for that keyword.

After 5 weeks of continuous dropping to about page 12 we started to back trace our steps. The first thing we did was reduce some on page optimisation i.e we realised we had added too many header tags with our keywords and too many of the keyword instances were in bold and as links.

Today our rank has gone up to page 2. I wonder if our back tracing was responsible or refreshing by Google's algorithms from their side as part of their regular SERP updates?

IN either case I am not complaining. Both reasons are true i.e Google updates its SERP often and ranking of websites fluctuate with it and also that over optimising a page can reduce ranking.