Certificates are used to provide identification to a web server. If there is a problem with the certificate, an error message will appear in your browser. To correct a Microsoft Certificate error you’ll need to update the root certificates on your system. Another option is to flush your DNS cache. You might need to reset your computer’s date and time settings if they are incorrect.

Updating Root Certificates in XP

1. Navigate to the Microsoft Download Center web page for the latest root certificates update (see Resources).

2. Click the “Continue” button and complete the validation check. Click the “Download” button and save the file to your desktop.

3. Double-click the file to run the program and update the Root Certificates on your system.

Get Updates in Vista/Windows 7

1. Navigate to the “Start” menu and then type “Updates” (without quotes) into the Search box.

2. Click the “Windows Update” link, located under Programs. The Windows Update dialog is displayed. Click the “Express” button to start the process.

3. View the updates that are available for your computer. Select any updates that are for Root Certificates or for Internet Explorer. Click the “Install Updates” button to install the updates onto your system.

Flushing the DNS Cache

1. Click the “Start” button and select the “Run” option. Type “cmd” into the text box and click the “OK” button.

2. Type “cd..” and press “Enter” to revert to the previous directory level. Repeat this step to go to the root of the C drive.

3. Type “ipconfig /flushDNS” and press the “Enter” key. This will remove any incorrect entries that have been stored in the DNS cache.

Reset Date and Time

1. Click the “Start” button and select the “Control Panel.” Select the option for “Clock, Language and Region.” Click the option for “Date and Time.”

2. Select the “Date and Time” tab. Click “Change date and time.” Select the arrow to adjust the hour, minutes and seconds, if the time isn’t correct.

3. Click the “OK” button after the time is adjusted.

Source: ehow