Unless you have more style sheets than that, you've messed up your break points:
#1 (max-width: 700px)
#2 (min-width: 701px) and (max-width: 900px)
#3 (max-width: 901px)
The 3rd media query is probably meant to be min-width: 901px. Right now, it overlaps #1 and #2, and only controls the page layout by itself when the screen is exactly 901px wide.
Edit for updated question:
(max-width: 640px)
(max-width: 800px)
(max-width: 1024px)
(max-width: 1280px)
Media queries aren't like catch or if/else statements. If any of the conditions match, then it will apply all of the styles from each media query it matched. If you only specify a min-width for all of your media queries, it's possible that some or all of the media queries are matched. In your case, a device that's 640px wide matches all 4 of your media queries, so all for style sheets are loaded. What you are most likely looking for is this:
(max-width: 640px)
(min-width: 641px) and (max-width: 800px)
(min-width: 801px) and (max-width: 1024px)
(min-width: 1025px)
Now there's no overlap. The styles will only apply if the device's width falls between the widths specified.