A discussion on three types of wireframe that have worked well in most situations:

Low Fi
Medium Fi
HiFi

Low Fidelity
Low Fidelity is created using XHTML—the real strength here is in the mark-up itself. There are a lot of advantages to properly marking up your elements to help streamline the understanding of visible elements. Lane use the code as a place to store meta information about the content itself. When rendered he keeps everything in a top-to-bottom listed format.

The Medium Fidelity Wireframe
This is the classic interpretation of the wireframe, simple black and white boxes with labels, an effective way to portray information to all the stakeholders involved. Something nice about medium fidelity is the ability whiteboard or sketch the concepts quickly in various mediums. The challenge is when you start putting too much time into a medium fidelity wireframe effort. It’s hard to know when a simple pencil sketch is actually a better solution then trying to recreate the sketch in Visio, Illustrator, or whichever tool you choose. There are a lot of ways to do the same thing with many different tools, but some do a much better job than others. When is it best to use it? When you really need to show how the information is visually arranged to help tell the story. Sometimes a list of all the elements isn’t going to be the strongest way to showcase the concepts. However, this is still an effective way to not get too busy and get in the way of the overall goal which is to be a simple representation of what your web site or application could look like.

The High Fidelity Wireframe
This is when you need to tell the whole story. It’s very close to creating the actual look and feel of the final deliverables being created. In fact, you should be able to create a site or application using these wireframes. This level of wireframe is much more closely aligned with something created by the interaction designer. The big difference here is that it’s still just a static representation. The interaction designer or developer would be responsible for creating the functionality in place.