Fitting title for iPhone

Could you teach me how can I change font size of title for fitting mobile device with keeping current size for PC.
I am still beginner of PHP. but I guess;
1.modifiy style.CSS file.
2.Insert condition sentense(If~).
If I am corrent, I also need function, which indicates the devise type.


1.modifiy style.CSS file.
2.Create new definition of title for mobile divice
2.Insert condition sentense(If~) of title in index.php

Is this right way? or something wrong?

Please help me.

Site is

This can be done much simpler as you can use CSS @media for this. You can add this code to Theme Options - Other - Custom CSS and it will apply styling for all devices smaller than 480px in width. You can change font size to any other one if you like but 30px should work just fine.

@media only screen and (max-width: 480px) {
  #site-title {
    font-size: 30px;

This is too cool! Thank you very much again.