var t = 0;

function up()
{
t += 10;

with(document.getElementById("content_text"))
{
if (t > 0)
t = 0;

if(style)
style.top = t + "px";
else
setAttribute("style", "top: " + t + "px");
}
}

function down()
{
t -= 10;

with(document.getElementById("content_text"))
{
if(t < -clientHeight)
t = -clientHeight;

if(style)
style.top = t + "px";
else
setAttribute("style", "top: " + t + "px");
}
}