You can add this script to master page to provide functionality throughout. Two main pieces which drives this are :
1. JavaScript ( to be placed in head tag )
2. HTML control/element to trigger the call to JavaScript function.
3. JavaScript ( to be placed at the end of the page, so that it can execute on page load )JavaScript( this will go in head tag ):
<script type="text/javascript" > function getCookie(Name) { var re = new RegExp(Name + "=[^;]+", "i"); //construct RE to search for target name/value pair if (document.cookie.match(re)) //if cookie found return document.cookie.match(re)[0].split("=")[1] //return its value return "" } setCookie = function setCookie(name, value) { document.cookie = name + "=" + value + ";path=/" //cookie value is domain wide (path=/) } function togglefn() { var e = document.getElementById('s4-leftpanel'); var e1 = document.getElementById('MSO_ContentTable'); if (e.style.display != "none") { setCookie('showLeftNav', 'no'); e.style.display = "none"; e1.style.marginLeft = "10px"; } else { setCookie('showLeftNav', 'yes'); e.style.display = "block"; e1.style.marginLeft = "155px"; } } </script>
HTML element ( some where in body tag):
<a href="javascript:togglefn();">hide/show</a
JavaScript( this will go towards page end ):
<script type="text/javascript" > var persistedLeftNav = getCookie('showLeftNav'); if (persistedLeftNav == 'undefined') { setCookie('showLeftNav', 'yes'); } else { if (persistedLeftNav == 'no') { togglefn(); } } </script>