从1.6开始，您可以使用便捷的方法:

From 1.6 onwards, you can use the convenient:

$('#myelem').css('left','-=8px')

如果由于某种奇怪的原因而被困在过去，请使用:

If for some strange reason you are stuck in the past, use:

$('#myelem').css('left', function(i,v) {
    return v - 8;
});

对于jQuery 1.4及更高版本.

for jQuery 1.4 up.