Is DNN search engine optimization friendly? Can i add an alt tag to pictures or make heading an H1 tag? If so how? And what else can one do with DNN to make it search engine friendly?

+1 to Cuong

Much of the SEO aspects of DNN are down to the selection of modules to use and the way in which you write your content.   The overall success of a DNN installation is down to the person setting up the website more than the platform itself.

You should concentrate on:

- SEO friendly skin, as Cuong says

- SEO menu - there are many available.  Spend the $30-40 on a good third party menu system.  The standard menu is not SEO friendly

- SEO Friendly Urls - make sure you turn on 'Human Friendly' urls as a minimum, but (self plug) you might want to look at a specialised Url Provider like the DNN Friendly Url Module that I develop.

- Don't use the 'create a link' function in FCK editor.  Learn how to write good <a> tags and write them yourself into the content.  Avoid using the 'LinkClick' functionality with Url tracking on.  Install a good analytics package for your site and use that to track visitors.

- Try and select content modules that put keywords into the Url, and look for modules that allow you to modify the title and description of a page.

Several good articles have been written about DNN and SEO.  Such as the DNN SEO Quickstart guide by Tom Kraak of Seablick consulting.   Read them all and then start building your site.  It takes more time to go back and modify a site than to do it properly in the first place.

You have to add an attribute to your web.config file, which is 'urlFormat="HumanFriendly"' '.  You need 4.6 or above for this.