I'd recommend to untick "allow reddit to show me custom styles" in reddit preferences and "Show this subreddit's theme" on the subreddit or else you may have a few glitches since subreddit styles can get pretty wild. I did very little to add compatibility with subreddit styles, partly to keep the code smaller and also because I can't be bothered.

I'd also recommend to disable RES night mode and other RES style tweaks for best color/style compatibility if you notice any inconsistencies. If you want the "filter visited links" RES tab to remain, choose "no" on the RES option. This will cause a tab overflow which won't look too great but function will still be fine.

Updates:
12/8 - Made the search page a bit more tolerable.
11/30 - /r/all is now filterable so updated its look and colored time of post submission.
11/26 - I did a bit to make RES more tolerable with this style. I don't use RES so I can't guarantee that part will stay updated much.
11/23 - Various small improvements and increased the font brightness a bit for the gray theme, as requested.
11/21 - My reddit styles are fixed, for the most part. I probably bit off more than I can chew with making my styles "dynamic" as it's essentially 6 styles that I'm having to maintain. But no worry, I'll still maintain this for the foreseeable future.
11/20 - A bit of a surprise lately. Reddit somewhat changed its CSS and userstyles.org has a new owner and with that, some styles were corrupted and mostly lost, mine included so I'll fix this mess eventually.
7/25 - Increased comment margin bottom paragraph by .4em. It was a small thing that bugged me for a while but never bothered to fix it. Comments will be a bit less dense but more readable, imo.
7/19 - A few more small changes to black and gray theme. Fixed the previous issue for now by limiting image size on the front page.
7/19 - Set overflow for thing and entry elements to visible, otherwise gifs were cut off. Doing further testing, that didn't work so well. I'll try to fix this at a later date.
7/18 - Darkened the gray theme a bit as suggested to add more contrast. Thanks for bearing with me for the small changes I've made lately. I believe I'm done for a while but I thought the style was in need of a few repairs and small changes that were long overdue. I only use and test the black theme consistently so for the others, I can't guarantee that there won't be minor issues with them.
- Improved comment .thing padding to give a bit more space. Should've done this earlier.
- Did away with overflow:visible for entries which was needed for RES image expansion. This helps give more consistency in the entries for those of us who aren't using RES. Still, I included it as an option below so if using RES image expansion, choose the RES option below.
- improved padding for blockquotes and scrollable mail icon
- A couple of RES color fixes. Sorry, I don't use RES anymore so I didn't notice. On a personal note, I started this theme when I didn't know as much about CSS and I realize now that the code is in proper need of a cleanup.
- Corrected an issue with wallpapers not showing up. Also fixed so the media-preview is centered. Did away with (RES Friendly) in the title because my fixes might possibly interfere with RES media previews, not sure as I haven't tested it.
- No, haven't abandoned it. Just a small update for side tables so they don't overflow + couple small fixes.
- Quick update for search input area over-extending.
- Spacing fixes. Not sure if I changed something or if it's reddit.
- Small fix for blockquotes on the black and gray theme
- Small fixes to blockquote and sidebar grippy.
- Made a small adjustment to RES live comment previews.
- Fixed it so when in window mode and using multireddit sidebar, the grippy would be covered by the scroll wheel. Current fix isn't the most elegant looking but it works.

Background art credits:
a1star - http://a1star.com (Star background)
xaddictedxtragedyx - http://xaddictedxtragedyx.deviantart.com (Pink Polkadot)
subtlepatters.com - Dark Denim & Light Cloth (http://subtlepatterns.com)
fullyillustrated - Space Battles (http://www.fullyillustrated.com)
Don Barnett - Halloween Pumpkin Background (http://www.donbarnett.com)
1-background.com - Christmas Background (http://1-background.com)

Thanks to reddit user cutcopy who did the original "web 2.0" mockup years ago that inspired others as well as myself to expand on it. Link: http://i.imgur.com/FiL29.png.

Also thanks to the creators of the other backgrounds whom I failed to find and to Imgur for hosting.

Want a dark scrollbar for Firefox? http://freestyler.ws/style/125814/firefox-black-scrollbar