How Do I Fix Yahoo! Error 403?
- 1). Submit your website to search engines once per week and not more. Submitting a site too often to search engines will produce a 403 error. This is the search engines' way of informing you that you are not following the submission guidelines and that you are on the verge of being banned because of spamming.
- 2). Check the sitemap submission frequency. Most search engines allow weekly submissions only if you have added pages or changed your content. Yahoo! allows submission of updated websites once every 48 hours.
- 3). Disable Internet Explorer "Friendly HTTP error messages." This will allow you to see a different error message, if one is applicable. Go to "Tools > Internet Options," then select the "Advanced" tab and remove the check from the "Show friendly HTTP error messages" box. Close your browser and try requesting the page again.
Source...