spun theme's css and responsive

http://yadayunikon.com/
I changed css (like header image’s position, slider’s position…) and it works with computer’s browser, but when I open my website with my cellphone, it’s kind a mess. what should I do now 🙁 somebody please help me!!!
Here is my css of header image:
.site-header img {
position: initial;
display: block;
float: initial;
margin: 20px 370px;
vertical-align: middle;
}