Hi jamalaljubory,
1) Do you get any error message?
2) Which web browser are you using?
3) Since when are you facing this issue?
4) Do you recall making any changes?
Method 1: Check if it works on another computer.
Method 2: If you are using Internet Explorer, you may try the steps mentioned in the link below
You cannot view, access, or load some webpages in Internet Explorer 8 or Internet Explorer 9 http://support.microsoft.com/kb/967897