Responsive Web Design

[TomClarke]

Responsive web design is an approach whereby a designer creates a Web page that "responds to" or resizes  itself  depending on the type of device it is being seen through. That could be an oversized desktop computer monitor, a laptop, a tablet or a smartphonescreen.
The purpose of responsive design is to have one site, but with different elements that respond differently when viewed on devices of different sizes.

[starsealsseo]

Responsive design is the name of the game, without it, your site's a relic, straight-up unusable on phones or tablets. Get your act together with fluid grids and adaptive images, or watch your bounce rate skyrocket.

You think users got time for a janky, zoomed-out mess? Nah, they'll ghost you faster than you can say "404." Mobile-first isn't a buzzword - it's survival. Stop cutting corners and rig up a site that doesn't suck on any screen. If you can't handle cross-device compatibility, maybe web ain't your gig.