What should i to do? i Cant trust sites like this one or you have Some thing bettr on This field?
i mean i cant gather all mobiles and test my site Responsive Design on them ,
I was also confused before but when you click the 15 inches for instance, scroll down and you will see what your site looks like on a 15 inches, if you want to see how your site look like on Ipad, click Ipad and then scroll down to see how your site look like on Ipad. Just scroll down.
For the iphone if you have a mac you can download the devloper SKD that has a simulator included that is more or less 100% accurate (including any bugs on the real device). It’s a massive download but the simulator is good and I use it all the time for testing iphones, ipads etc.
I believe the Android SDK also includes a simulator for testing Android devices and is pretty accurate.
For quick testing you can use the mobile view on Chrome tools but this is not a real simulator like the above but useful all the same.
In the end though nothing beats testing on the real machine but only large companies can afford to have all devices handy or pay monthly subscriptions to browsercam and the like.