Use the preview functions to view pages before publishing them. This allows you to see how they will look once published and make any necessary adjustments before publishing the page.
While editing the page, click Preview (on the page action bar at the bottom of the page).
If the Preview button is not there, speak to your site administrator. It may be that they have turned off access to the button for this page type or it may be that the page type does not allow previewing (such as with Category pages).
While editing the parent page, go to the Child Pages tab.
Locate the page to preview in the list of child pages and click the Preview link on the right hand side.