In the Page Backgruond dialog box you can customizebackground for the page. Otherwise, the background settings will be taken from the current style, if any, or from the default settings in viewer's browser.

You can set both image and color when setting a backgound.

If you want to set an image as a background, check the Image check box.
The image selection window has three tabs:

You also can import any image file by clicking the Import... button, and create a new image by clicking the Create button. All changes are immediately previewed in the Preview window.

In the Horizontal Position and Vertical Position sections, set the image position on the page.
To have a background composed of the tiled images, check the Tile boxes.
To place the only image, clear the Tile box, and select the position: Left, Center (horizontal), Right, Top, Center (vertical), Bottom.

Check the Watermark box to set the image to remain in the same position in the browser window when the viewer scrolls the page.

If you want to set a background color, check the Color check box.
Select Color Library, and a color from palette.

Check the Margins check box to set the indention figures for text from the Left and Top of the frame. Set up your figures in pixels.