Hi Anne,
This is a Drupal behaviour. When you enter some text into a piece of content, like the body of your new page, Drupal runs a set of "filters" against the text. These change the text in several ways, e.g. converting your line breaks into HTML line breaks, automatically inserting links etc. The filters also perform some "clean up" on your text to ensure you have not put anything you are not supposed to in. The default behaviour is that images and tables are stripped out - firstly to prevent malicious images being posted and secondly because web standards gurus generally don't like tables being used to create page layouts (they are supposed to be for tables of information not layout). Remember that many Drupal sites will have content input by lots of site editors so the default behaviour is perhaps more strict than you need on a site with just yourself editing.
There are 2 ways around this. First, you can change the input format of your content - the section for doing this should be on the Drupal edit page just below your body text. Expand the Input Formats section and change to Full HTML then save the page - this allows any HTML to pass through unfiltered. A better way might be for you to change the "Filtered HTML" input format. Log in as admin and go to Site configuration > Input formats on the admin menu. Click the configure link for filtered HTML. Now go to the Configure tab. In the Allowed HTML tags box, add "<img> <table> <thead> <tbody> <tfoot><tr><th><tr>" to the end to enable images and tables in your content, then save the input format.
Best wishes