reason: if you use a link or multiline column in a SP List and type in a web-url, by clicking it on, the new url will be loaded in the parent window as your SP Collection or portal is. To avoid this behaviour e.g. the url begins with http or www  can be loaded in a new window or browser tab. 

solution:  open the SP Designer and select the appropriate SP list you want to extend with this functionality. Select the default view or another by right-clicking an open that in advanced mode. 


and place the following code after the content place holder main don't forget to download and/or register jQuery !!!!:

<asp:Content ContentPlaceHolderId="PlaceHolderMain" runat="server">
<script type="text/javascript" src="/Scripts/jQuery-1.11.0.js"></script>
<script type="text/javascript">
$(document).ready(function() {
    var link = $(this);
    var url = link.html();
    //Link contains http or www or something else......
    if ((url.indexOf('http') !== -1) || (url.indexOf('www') !== -1))
   		return false;