Fundamentally a web design has to convey a message or project a clear definition of meaning to the user within the first few seconds of landing on your site. Without a hook the chances are high that the user will simply pass by your site and will be just as quickly forgotten.
A popular trend at the moment is headline grabbing over-sized typography. This type of hook is unmissable and it helps the user focus there attention instantly on your site.
Now, there is a right way and a wrong way to do this – you can't just change your CSSes <h1> tag to 100px – and the typography showcases below show you how it can be and should be achieved.