This is the definitive guide to WordPress overkill or how not to spend your night sleepless trying to figure out what the heck is wrong. Remember, every blog is unique and as Matt says, chances are there’s no one in the room with the same plugins installed. If you get yourself in a situation where you home page is not loading but the mobile version of the blog is working fine or suddenly WordPress admin has no CSS loading keep reading.
WordPress theme developement guidelines mentions “A theme can optionally use a functions file, which resides in the theme subdirectory and is named functions.php. This file basically acts like a plugin, and if it is present in the theme you are using, it is automatically loaded during WordPress initialization (both for admin pages and external pages)”.
In a nutshell if there is anything wrong with your blog and you even remotely thought of changing anything in functions.php (resides in your theme’s folder) go back and undo. Functions.php is very important to your WordPress blog, way more important than you think it is. If you mess functions.php, prepare for no loading errors and downtime unless you know what you’re doing or you know others who know what to do.
No CSS in WordPress admin
There are not enough reasons for WordPress to go all blank and vanilla in the admin area. If that happens make sure your web server’s Mimetype is properly declared and assigned. Caching and minifying CSS issues can get your blog CSS naked but not the admin area. Make sure you try at least one vanilla web server config before going into the trouble of uninstalling all your plugins and ask for help on the WordPress forums.
Don’t rush plugin updates
We all want to run the latest and greatest version of WordPress and plugins but there are times plugins can bring the world down. Unless the new plugin version fixes a major security hole, wait for a few days after each new release and update late. You need to avoid the situation where a tiny, stupid bug brings down your blog because it conflicts with certain plugins or plugin configuration you only have installed. Installing an older, not outdated, version of a plugin is a good way to test proof.