Salar is right - the response to the DNN Nav menu probably isn't what the core team direction has hoped for, more people use the solpart menu, but partly that's becuase it's 'safe' - it came out of the box and has been that way for years, the menu itself has been updated, and in the process along the way - I think there was an attempt to do things with a menu that didn't use up as many resources, and, could be used without tables. The DNN Menu when rendered in a horizontal method, doesn't use tables.
But further than that, we've seen much more growth in the area of menu development, from the Rad menus provided by telerik, through to the CSS menus like the house menu and there is the 360 one on snowcovered and John Mitchell's CSS Menu too. These solutions use CSS only and are more 'true' navigational options that are in keeping with other technologies.
I did what I could with the limited resources and no doubt you've probably already seen this - http://www.skincovered.com/dnn-menu.aspx and this - http://www.ninasfreeskins.com/xdnnlight/home.aspx which is a free skin using the nav menu.
I have tried very hard over the few short years of DNN to provide a few solid, well structured free skins and information to make the journey of skinning more accessible, and I know it's not much in the whole scope of things by comparison to module developers and code out there, and I wish I could do more with the resources I have, but it's often a matter of taking small steps at a time and trying things out. Armed with the skinning documentation and some free skins, you should be able to grasp a basic understanding and then move forward from that.
The DNN Nav Menu is ok - I don't know why it was put in except some move forward in some way - who knows, but to date, I don't see any commercial skins coming out with it at the moment, and I can tell you from my experience, I was never able to make it do what it should do.
That's just my thought on this - I've done alot of projects, in the hundreds now and have never been asked about using the DNN Nav menu. My clients just want it to work, look good and be easy to install, and I'm sure that Salar would also agree, there are things we just don't put into skins because they aren't used or called for.
If I were you I'd stick to solpart menu, or look at third party options for a solution.
Hope this helps you too.
Nina Meiers
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