A Web page is not a book nor even a magazine article. By default, there are half inch margins on a browser page. I'm not sure if that is the most pleasing configuration for reading. Another choice is to use a 3-column table to set your left and right margins. They can be set as a percentage of the screen to account for different sized monitors.
Some pages use a relatively thin column of text, similar to that seen in a print magazine.
This does not look that bad but is a pain when printing. Experiment with different column widths to find what suits your Web site users the best. In conclusion You should make considerations about how readable your Web page is for your audience. Use a good combination of background and typeface colors. Be cautious about using wild background images that may interfere with the text.