Improper HTML - so I don't know if any solution would be cross-browser compliant...
step 1: update your style sheet so that div1 is hidden by default
e.g.,
#div1 {display:none;}
step 2: add an onchange handler to your <select> and give it an ID
e.g.
<select name="selection" id="selection" onchange="checkToSeeIfIShouldShowRow1()">
step 2: write your javascript function for checkToSeeIfIShouldShowRow1
e.g.
function checkToSeeIfIShouldShowRow1() {
var selectedValue = document.getElementById('selection').value
if (selectedValue == '2'){
document.getElementById('div1').style.display='inline'
}
}