js_get_pageInnerWidth

function js_get_pageInnerWidth(){

// http://www.quirksmode.org/viewport/compatibility.html

if (self.innerHeight) // all except Explorer
{
y = self.innerHeight;
}
else if (document.documentElement && document.documentElement.clientHeight)
// Explorer 6 Strict Mode
{
y = document.documentElement.clientHeight;
}
else if (document.body) // other Explorers
{
y = document.body.clientHeight;
}

return y;

}