Its a common problem for most printers and not a fault as such. It is the way that websites are displayed on the screen in pixels. These do not equate to DPI (Dots per inch) that the printer uses.
Some printers, Canon for instance have a setting for printing web pages in full by adjusting the size down to fit the page. You can try using Landscape setting or, Scale to fit if your printer has this setting. Another method that sometimes works is to set your margins from the edge of the text instead of edge of page then reduce the margins as far as they will go.