I think I accidentally deleted all the certificates. Now everytime i open a site, the internet exploer will ask me if I want to "view content". Besides this, sometime a question will pop out, asking me if i want to preceed with the current site. My google chrome and firefox don't work too. I have not use any resources to try to fix it yet. My computer is Windows 7 home premium 64 bit,using IE 9. I find this really frustrating because the pop ups are really annoying and clicking it everytime i refresh the page make my patience run out. I hope there is a way to recover the certificate or add the certificate for sites I trust. It will be good if there is some certificate that I can download, maybe from microsoft. Thank you

Try installing this update for Root Certificates: http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=3237. You "might" also be able to get them back by using Windows Update. That is assuming this is your actual issue. Possibly you just need to add to your Trusted Sites list, but I am going with your self diagnosed issue. Please, let us know if that resolves the issue.