The controls used to navigate this site depend on the device you're using. Wherever links are presented as a numbered list (search results, help index) you can use the number keys on most mobile phones to access links directly.
Most pages don't have a link back to the previous page - instead you should use the back button on your browser. Some mobile phones have a dedicated 'back' key, whilst on others you should look for the back feature displayed on one of the 'soft' keys.