I suspect the cause of the problem – if your visitors use IE – is the page setup within IE. Typically the defaults are something horrendous like 25mm margins left and right which doesn’t leave much room in between. When they go to print a page, the print width is determined by the widest fixed-width item on the page, and in your case I believe it is the top graphic. (See the attached for where this setting is made.)
I notice also you have set the width for 800 wide screen resolution, as opposed to the expand-to-fit layout of (eg) this web page.
Suggestions:
1] Change the layout of your page so that the width is set as a percentage rather than a fixed width – probably not easy if you want to keep the style and images you have.
2] Create a printable version of the page which does not have the same wide image on it – click on the icon top right of this post to see how the Lounge offers a ‘cleaner’ version to print.
3] Add “How to print this page” instructions – the user needs to reduce their margins or set the page layout to Landscape.
**Edited to add: Note that the page setup for IE affects how Outlook prints by default – set it to Landscape and emails are also printed out in Landscape format…..