function NewWindow(page, name, ancho,altura)
{
    var vwidth=850;
    var vheight=750;

    if ((screen.width<=1024) && (screen.height<=768))
    {
       vwidth=850;
       vheight=720;
    }
    if ((screen.width<=800) && (screen.height<=600))
    {
       vwidth=800;
       vheight=600;
    }

    if ((screen.width<=640) && (screen.height<=480))
    {
       vwidth=640;
       vheight=480;
    }

    var esNN4="yes"
    if(navigator.appName=='Netscape'){esNN4="no"};
    topx= screen.availWidth/2 - vwidth/2; 
    topy= screen.availHeight/2 - vheight/2; 
    
    OpenWin = this.open(page, "NewWindow", "toolbar=no,menubar=no,location=no,address=no,scrollbars="+esNN4+",resize=no,width="+ vwidth +",height="+ (vheight - 35) +", Top="+ topy +", left="+ topx);
}