function changeImage1(){
    document.myimg.src="images/bg/bg_kareshi.jpg";
}
function changeImage2(){
    document.myimg.src="images/bg/bg_titi.jpg";
}

function changeImage3(){
    document.myimg.src="images/bg/bg_kanojo.jpg";
}

function changeImage4(){
    document.myimg.src="images/bg/bg_haha.jpg";
}

function changeImage5(){
    document.myimg.src="images/bg/bg_tomo.jpg";
}
function changeImage6(){
    document.myimg.src="images/bg/bg_kanreki.jpg";
}

function changeImage7(){
    document.myimg.src="images/bg/bg_syussan.jpg";
}