Before telling you how to install it, I think I should have to tell you what a deviantSkin exactly is.
A deviantSkin is a modified CSS file that affects the layout of a webpage.

Unfortunatly only firefox users can use these files.
So, yet another reason to Get Firefox.

Edit: seems like Opera users can use these skins as well..
scroll down to find out how to install them.

In the deviantSkin gallery here at deviantart in the first place.
Beware: this gallery still contains a lot of dAv4 skins. And they won't work anymore.

Also, @bluespeed9 will be making a list of dAv5 skins in his journal.

There are a bunch of different methods to install a deviantSkin.
I'll try to show and explain all of them as good as possible.


Using Stylish recommended method !

1. Download and install the Stylish Extension

2. Click on the Stylish icon in Firefox. Choose "Manage Styles..."

3. Click "Add..." Give it a name and write this line:

@import "url to the css file" ;

4. Save and enjoy.


This is the recommended method, since the stylesheet will be automatically updated when the author of this stylesheet posts a new version..

To Uninstall:Disable the stylesheet or simply uninstall the stylish extension.


The deviantSkin Extension

1. Download and install @bluespeed9's deviantSkin Extension

2. After restarting firefox and donating him some cash ( ), right-click the little icon in the bottom-right corner of your browser.

3. Go to 'skin manager'.

4. Click the add skin button and copy the link to the css file in the textbox.
( the css file is the deviantSkin )

5. Press OK, restart firefox and admire your newly installed deviantSkin.

6. Take a peek at the deviantSkin options, some usefull stuff over there.

To Uninstall: Apply the default deviantart skin in the skin manager..


Using Stylish for coders.

1. Download and install the Stylish Extension

2. Open the css file ( just click the link to the css file.. )

3. Select all, and copy.

4. Click on the Stylish icon in Firefox. Choose "Manage Styles..."

5. Click "Add..." Give it a name and paste the code.

6. Save and enjoy.

To Uninstall:Disable the stylesheet or simply uninstall the stylish extension.


userContent.css

1. Go to your documents and settings > your username > application data ( a hidden folder ) > Mozilla > Firefox > Profiles > #something random#.default > chrome

2. Download the css file (right-click, save link as )

3. Make sure that the name of the file is "userContent.css" and save it in the chrome folder.

4. Restart firefox and admire.

To Uninstall:Rename, remove or empty the userContent.css file.


For Opera Users

1. Download the css file ( save it to yoru harddrive ).

2. Go to the frontpage ( [link] )

3. Right-click the page and select "Edit site preferences..."

4. Change the URL from "www.deviantart.com" to "deviantart.com"

5. Go to the "Display" tab and select the previously downloaded css file.

6. Hit ok, refresh and enjoy.

To Uninstall: Go to Tools > Preferences... > Advanced > Content > Manage site preferences...

Credits to ~Deko-Drak for this very usefull information.