problem with div and display

problem with div and display

Hello,

i've got a problerm with the display of some divs with this function :

function switch_divs_mobile()
            {               
                if( document.getElementById("div_home_mobile").style.display == "none")
                {
                    document.getElementById("div_home_mobile").style.display = "block";
                    document.getElementById("div_titre_mobile").style.display = "none";
                    document.getElementById("div_contenu_mobile").style.display = "none";
                    alert("1");
                }
                else
                {                   
                    document.getElementById("div_home_mobile").style.display="none";
                    document.getElementById("div_titre_mobile").style.display = "block";
                    document.getElementById("div_contenu_mobile").style.display = "block";
                    alert("2");
                }
            }

When I use it the first time i arrive on a page, i'm in the first case (if... == "block") and it works only for the div_titre_mobile (its display go to "none" ) but not for the 2 others.

If I use the function another time, it's the same, it works only for the div_titre_mobile (this time its display goes to "block") but not for the others.

If I reload the page, there is no problem, everything works.

I tried to write my function in many ways in jquery (show, toggle...) but the problem is exactly the same.

Who can help me ?

PS: sorry for my english