Beyond the standard features of ArcGIS Online, there are some advanced capabilities to customize the look-and-feel of your portal home page. Using CSS instructions, you can redefine some of the Esri default styles in order to get a more attractive page to welcome the users of you portal. Here is an example: http://demoagol1.maps.arcgis.com
If needed, I can provide the CSS source I used for this demo.
Thank you for your file, it's wonderful. I have only one question, how could you able to add more links at the bottom of home page although it's only allow either a link or mailto?