It is important that your website can be viewed correctly on the device the viewer is using. These days there are so many different devices people use to look at websites that it has become much more complicated to design a website that can look good across allof these devices. When you think that the same website needs to look good on a mobile phone screen as well as reformat itself to look good on a 4K display you can understand why.
Consider that a standard smart phone has a screen resolution across of about 400 pixels and a 4k UHD display has has a screen resolution across of 3840 pixels. A website needs to be an adaptive display to rearrange itself to suit these different screen sizes. It also needs to scale down to a lower resolution display without losing design and content assets.
Allcorp websites are custom coded so that they display themselves and their individual design attributes across all screen sizes.
There are some website designers that say they make responsive websites who aren't doing the complete process and discounting the new generation of UHD displays that are beginning to become the norm.
While their websites do act in a responsive way from the standard HD monitors and down to tablets and phones they don't make the websites also act in a responsive way to UHD displays. UHD displays include new generation PC's which are 4K as well as all new Mac computers that are 5K displays.