function tabOver(t)
{
    switch(t)
    {
        case 'block_a': document.getElementById('block_a').style.backgroundPosition="0px -66px";
                        break;
        case 'block_b': document.getElementById('block_b').style.backgroundPosition="0px -99px";
                        break;
        default: return;
    }
}
function tabOut(t)
{
    switch(t)
    {
        case 'block_a': document.getElementById('block_a').style.backgroundPosition="0px 0px";
                        break;
        case 'block_b': document.getElementById('block_b').style.backgroundPosition="0px -33px";
                        break;
        default: return;
    }
}
function tabOverMember(t)
{
    switch(t)
    {
        case 'block_a': document.getElementById('block_a').style.backgroundPosition="0px -165px";
                        break;
        case 'block_b': document.getElementById('block_b').style.backgroundPosition="0px -231px";
                        break;
        default: return;
    }
}
function tabOutMember(t)
{
    switch(t)
    {
        case 'block_a': document.getElementById('block_a').style.backgroundPosition="0px -132px";
                        break;
        case 'block_b': document.getElementById('block_b').style.backgroundPosition="0px -198px";
                        break;
        default: return;
    }
}