We got numbers of requests for fixing errors of skins sold by other people or companies. If you are not familiar with Dotnetnuke skin structures, you better buy skins from some companies has support. A number of factors can break your skins:

1. A Dotnetnuke version upgrade (for example the recent changes of DNN 4.5.3, makes 90% of the skins with search functions not displaying correctly. No matter how good and how many experience a skin design company has. A new skinobject is not predictable. It is easy to fix, but can you expect every company go fix every their skin and give you an update?)
2. A browser upgrade (when Browser Company release a new version of browser, they may choose to handle the HTML or CSS differently. That means a well working skin could not working because your client is changing the browser, IE6, IE7, Vista, Opera, Firefox, Netscape, Safari all handle differently. Do not trust when someone indicate it is tested under different browsers. It's always going to happen no matter how good your current skin is. Tomorrow you need someone to make sure it is still working correctly)
3. A new logo, a new banner, flash could break your skins as well.
4. A new module may make your skins does not look perfect anymore.
5. Technology changes, web standard changes.
6. Light background skin gives you less problems. If you want buy from a stranger. Buy the light background skin. It will work 90% of the modules. Unless you use "TEXT/HTML module”, you do not have control over some module’s displaying. Even some of the core module use hard coded colors like white, black, light gray. Those modules will works fine for light background skins. But for dark background one; you need to fine-turn some css to make it work correctly. That is very time consuming works. Unless you know CSS very well, it is almost impossible to make it work correctly.
7. Send Email to the seller before you buy. If you are not familiar with some new seller, ask them questions before you buy.