I believe your wrapper may be causing the issue. Instead of setting a fixed width for the object do:
.wrapper {
max-width:900px;
width:100%;
display:block; //for centering
margin:0 auto // for centering
}
Should solve your problem and make the website more responsive throughout different platforms. Good luck! :)
NOTE
If you are not already doing so, take rajkumar's comment and add:
<meta name="viewport" content="width=device-width, initial-scale=1">