function changeDivImagea() 

{ 

    document.getElementById("display").style.background = "url(./portfolio/edu2a.jpg)"; 

} 

function changeDivImageb() 

{ 

    document.getElementById("display").style.background = "url(./portfolio/edu2b.jpg)"; 

} 

function changeDivImagec() 

{ 

    document.getElementById("display").style.background = "url(./portfolio/edu2c.jpg)"; 

} 
function changeDivImaged() 

{ 

    document.getElementById("display").style.background = "url(./portfolio/edu2d.jpg)"; 

}