If your navigation contains many links and comes before the main content in the DOM, add a Skip to main content link before the navigation (for a simple explanation, see this A11Y Project article on skip navigation links). Using the .sr-only class will visually hide the skip link, and the .sr-only-focusable class will ensure that the link becomes visible once focused (for sighted keyboard users).
Due to long-standing shortcomings/bugs in Chrome (see issue 262171 in the Chromium bug tracker) and Internet Explorer (see this article on in-page links and focus order), you will need to make sure that the target of your skip link is at least programmatically focusable by adding tabindex="-1".
In addition, you may want to explicitly suppress a visible focus indication on the target (particularly as Chrome currently also sets focus on elements with tabindex="-1" when they are clicked with the mouse) with #content:focus { outline: none; }.
Note that this bug will also affect any other in-page links your site may be using, rendering them useless for keyboard users. You may consider adding a similar stop-gap fix to all other named anchors / fragment identifiers that act as link targets.