To change default print margins or header/footer in Mozilla Firefox, click on the Firefox drop-down menu in the upper right corner of the browser (three horizontal lines in the newest version of Firefox), then click on Print.
At the top of the screen that appears, click Page Setup, and then click on the Margins & Header/Footer tab.
Manually change Top, Right, Bottom, and Left margins to 0. Note that this will change the defaults for all web printing from Firefox.
Change print margins in Chrome using the "Margins" drop down menu in the print dialogue that opens when you click "Print Form", type Ctrl + P, or select Print from the browser's tool menu.
Select None. Chrome will remember this print setting for the session, but will change back to 0.4" default each time a new session is opened – that is, each time the browser is closed out completely and reopened).
By default, Chrome puts the document title and date in the header, and the URL and page numbers in the footer. You can instead specify that no information appear in the header and footer by unchecking the Header and Footer box in the print dialogue. As with margins, Chrome will remember your setting within a single session, but will change back to defaults when a new session is opened.