CSS media queries min-width and min-device-width conflicting?

Question

I am very new to the world of media queries, and it's clear there's something fundamental I'm missing about the difference between width and device-width -- other than their obvious targeting capacities.

I would like to target both regular computers and devices with the same breakpoints, so I just duplicated all of my min & max width queries to min-device and max-device width queries. For whatever reason, when I add the -device counterparts, my CSS is interpreted very differently by regular computers, and I'm not sure what I'm doing wrong.

You can see the effects here (this is what it SHOULD look like)

And here (after adding -device-width to my queries, my CSS gets screwed up at the smallest width -- the larger resolutions are seen even when the browser width is smaller than what is getting called).

Here are my CSS links -- is there something wrong with my syntax? :

<link rel="stylesheet" media="only screen and (max-width: 674px), only screen and (max-device-width: 674px)" href="300.css">
<link rel="stylesheet" media="only screen and (min-width: 675px) and (max-width: 914px), only screen and (min-device-width: 675px) and (max-device-width: 914px)" href="650.css">
<link rel="stylesheet" media="only screen and (min-width: 915px) and (max-width: 1019px), only screen and (min-device-width: 915px) and (max-device-width: 1019px)" href="915.css">


<link rel="stylesheet" media="only screen and (min-width: 1020px), only screen and (min-device-width: 1020px)" href="1020.css">
<link rel="stylesheet" media="only screen and (min-width: 1200px) and (max-width: 1299px), only screen and (min-device-width: 1200px) and (max-device-width: 1299px)" href="1200.css">
<link rel="stylesheet" media="only screen and (min-width: 1300px), only screen and (min-device-width: 1300px)" href="1300.css">

Answer 1

Device-width refers to the display's resolution (eg. the 1024 from 1024x768), while width refers to the width of the browser itself (which will be different from the resolution if the browser isn't maximized). If your resolution is large enough to get you in one break point, but the width of the browser is small enough to get you in another one, you'll end up with an odd combination of both.

Unless you have a legitimate reason to restrict the style sheets based on the resolution and not the size of the viewport, then just use min-width/max-width and avoid min-device-width/max-device-width.