According to About.com, a 403 error is an error occurring within a browser when access to a specific page or resource is completely forbidden. Checking the URL entered, clearing the browser's cache and cookies or logging on to the site are some possible ways to fix the issue.
A 403 error can be fixed in a multitude of ways. Firstly, clearing your browser's cache and cookies through the settings can help this issue. However, it is common for users to type in a URL incorrectly, resulting in a 403 error. Ensure the URL is completely correct before attempting another solution.
If neither of these steps fixes the issue, it may be necessary to contact the website directly; contact information for some popular sites can be found through The Website Contact Information page on About.com. Using Twitter to contact a page's social media team often works as well.
If the 403 error persists, contact your ISP and verify your public IP address or ISP has not been blacklisted; blacklisting results in 403 errors across an entire website. If the website is working for other users, you may have been blacklisted.
If all else fails, try visiting the website at a later time. The website may be performing maintenance or may have a downed service; this is especially true if no one else seems able to access the site in question. Visit the page regularly until you can access it.