How to highlight new added links on front page with cookies?
You could do this in a limited way where you store each item's nid and updated date in a cookie. The cookie would get updated each time the user loads the front page by JavaScript that reads the nid and date from the DOM. 

Before the cookie is updated it is used to set a highlight class on any items that aren't set in the cookie. 

In order for the cookie to not grow too large the items could be pruned by date if the front page only shows most recent. 

For an demo take a look at https://jsfiddle.net/rnc2eLxr/2/

I've included the code below.

JS libraries:


https://code.jquery.com/jquery-2.2.4.min.js
https://cdnjs.cloudflare.com/ajax/libs/jquery-cookie/1.4.1/jquery.cookie.min.js


HTML:

&lt;body&gt;
  &lt;div class="view"&gt;
    &lt;ul&gt;
      &lt;li class="link"&gt;&lt;a href="http://google.com" data-nid="1" data-date="2017-01-01"&gt;Google&lt;/a&gt;&lt;/li&gt;
      &lt;li class="link"&gt;&lt;a href="http://reddit.com" data-nid="2" data-date="2017-01-02"&gt;Reddit&lt;/a&gt;&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/div&gt;
&lt;/body&gt;


Javascript:

// Get cookie value.
var linksString = $.cookie('frontLinks'),
  links = [];
if (linksString != undefined) {
  links = JSON.parse(linksString);
}

// Highlight any links not found in cookie.
$('li a').each(function(i, v) {
  var $link = $(v),
    tuple = {
      "date": $link.data('date'),
      "nid": $link.data('nid'),
    },
    match = findByNid(links, tuple.nid, true);
  if (!match) {
    $link.addClass('highlight');
    links.push(tuple)
  }
});

// Find array object by nid property.
function findByNid(inArr, nid, exists) {
  for (i = 0; i &lt; inArr.length; i++) {
    if (inArr[i].nid == nid) {
      return (exists === true) ? true : inArr[i];
    }
  }
}

// Store links in cookie.
$.cookie('frontLinks', JSON.stringify(links))


CSS:

li a.highlight {
  border: red 1px solid;
}