A problem with background-attachment: fixed;

[igor-tv]

If I use code:

.main {
    display: block;
    margin: 0 auto;
    width: 1000px;
    background: url(../images/bg.jpg) no-repeat;
    background-attachment: fixed;
    background-position: top center;
}

            $('.textbox').blurjs({
            source: '.main',
            radius: 20,
            overlay: 'rgba(255,255,250,0.4)'
            }); 

blur.js incorrectly calculates the background-position: top center; position of the .textbox 's blured background. I have blured window not at the same location then background of .main

Blur background position depends on the width of the browser window.

[MurhafSousli]

I have the same problem, but it only happens on chrome, but works on ff and ie