The size of your graphic images dramatically affects the download time of your site, so keeping images small is a good idea. If you make an image smaller simply by using the drag handles, though, you haven´t actually changed the size of the image file, so that´s no good as a way to speed up the download time.

What you need to do is resample the image.  You do this by selecting the image, going to the images toolbar and selecting the Resample tool! Now your image file has changed to match the actual size of your graphic.

You could, alternatively,  choose to create a Thumbnail, which is a tiny image that allows the reader to decide whether to see the bigger version or not.  

Just select the image and then choose the AutoThumbnail button on the pictures toolbar. 

FrontPage automatically creates the thumbnail, inserts it in place of the larger image, and creates a hyperlink to the fullsized image from the thumbnail.

 Not difficult at all: just try it!