How to fix certificate error in Internet Explorer 8

Hello,
I just got my laptop fixed and now many of the sites that I always go to are saying that there are certificate errors or that the security certificate is expired or not yet valid, etc... Why is this happening or is there a setting that can change this?
The main reasons for Internet Explorer certificate errors are:
• The computer's date is set to a wrong value
• The Security Certificate has really expired
• The web-site is not trustable
The most common reason could be the computer’s wrong date. Because the security certificate is valid for a certain period of time. So if the time is incorrectly set on your computer, you may receive this security certificate error message when browsing sites. So the first thing you are supposed to do is to check the date on your computer. Usually, after setting the date correctly, you can access the sites normally. If not, the security certificate of the website may really have expired or the website is not trustable. So never put your important login ID or password on such pages if you see the Security certificate error.

Set the website as trustable one?

If you are sure the website is trustable, you can manually set it as a safe website on your Internet Explorer to view it successfully.
1. Select Tools->Internet Options.
2. Select Security->Trusted sites->Sites.
3. Confirm the URL matches, and click "Add" then "Close".
4. Close the "Internet Options" dialog box with either "OK" or "Cancel".
5. Refresh the current page
Then you can access the website now. If you don’t want to set it as a safe website, you also can remove it from the list of trusted sites from your Internet Explorer.

1 click to remove IE errors

If the solution above can't  help, there may be  IE errors in your system files. You can't find it by simply opening and checking system files. Using a PC system maintenance tool to perform this work will be more convenient and effective. If you still haven't a choice, Wondershare 1-Click PC Care can be nice option, which can do this job within 1 click. Download and install it on your computer, then it will automatically check all errors out and you only need to give one click on the "Fix Now" button. All problems go out of your computer.

Source:-http://www.wondershare.com/disk-utility/internet-explorer-certificate-error.html