[Lampard]

great web design is a must . but dont forget the user experience . good web desing need a great user experience of using it . make the design that is easy to use and can give the user great experience .

but some of the great design really slow old device down espescially the website that have lot of heavy css and javascript

That depends who is programming it
You can even make a great looking website and that will be also compatible with old devices.