part 1 – http://digitalzoomstudio.net/2011/02/23/problems-i-had-as-a-wordpress-developer-with-badly-coded-plugins/
Or THEMES. As you may know, I sell premium WordPress scripts here – http://codecanyon.net/user/ZoomIt/portfolio?ref=ZoomIt . As authors, we are not required to offer support, but I myself consider it a important part of the deal and I do offer it best as I can. 80% of support requests are related to plugin compatibilities ( the other 20% are free modifications attempts from buyers or buyers who do not read the docs ).
Multiple jQuery Loads
I have had countless support requests where my jQuery plugins would not work. The reason was 90% the same – the user had a second ( even 8th ) instance of jQuery loaded. What this does is ovewrite the jQuery reference from memory and my plugin left in a old object which is not the actual jQuery reference now.
Solution – http://jsbin.com/useyis/14/edit
IE9 Stylesheet Limit
Spent a lot of time before discovering this. Never would have crossed my mind. IE9 and below has a 32 bit stylesheet limit. Which means you can only load 32 stylesheets. Wow
– use less stylesheets ( doh )
– OR use a minifying plugin like W3 Total Cache which combines all of your scripts / stylesheets into one.