Till yesterday my blog was ranking very high for lot of keywords but today no results?

Search engines are sometimes very fickle. One day you can rank very high, and the next is not so good. As long as you maintain your visitor numbers, you will rank well within them. I would however recommend going out there and getting a bunch of backlinks to your blog. Comment on other blogs making sure that you link to your blog in the comment. This will increase the number of visitors as well as show that your blog has validity.