By default WordPress creates ugly URLs containg a question mark and numbers for your permalinks and archives such as “http://yourdomain.com?p=123″. You must change it to make it more friendly to both users and search engines. It is best to optimize your blog for maximum keyword density. A simple way to do this is to change to a custom permalink structure.
In your WordPress admin area, on the left hand side scroll down to settings and click “Permalinks”. Select “custom structure” in the Customize Permalink Structure area and in the box enter:
This will create URLs for your permalinks and archives that would look like this:
Click “Save Changes” to save this setting.