You are probably thinking about your content wrong. If you're thinking about content as simply content, you'll err on the side of too much.

Don't think of your content as text or paragraphs, but as units of information. A sentence can be a unit of information just as much as a single word in a menu. This shift in thinking will dramatically change the way you create and present content. As I'll explain later, irrelevant units of information devalue that which is most relevant to the user.

This shift in thinking will dramatically change the way you create and present content.

1. Navigation

The human mind is only capable of taking units of information in chunks of 3-7. Take a look at the following two examples:

The second phone number is much easier to take in and memorize because it is broken up into chunks. If your menu has too many options, the user will have a very difficult time getting to where they need to go.

If your system has thousands of menu items, utilize an intuitive hierarchical category system and implement advanced search. Example: amazon.com 

2. Dialog Boxes.

Information overload. Dialogs should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialog competes with the relevant units of information and diminishes their relative visibility.

3. Page Items

Each block of information vies for user attention. Users subconsciously blind themselves to anything that looks like an ad.

The Yahoo! homepage has fifteen different macro information units, or blocks, for me to choose from, which is a bit overwhelming.

The BBC homepage, however, has only 8 information units that I'm choosing from - with much better headlines.

4. Links

Too many choices paralyze users. Shopping for an apple computer is easy because you have less than a half-dozen models to choose from. A PC, however, can be a nightmare with hundreds of options.

If your link strategy is just a page littered with "click here", the user will feel overwhelmed, especially if the links don't explain where they go. And for the record, nothing that says "click here" explains were the user goes. Learn more about writing better links.

Bonus tip: Make links self explanatory.

In the first example, the user will read click here, and will have to backtrack in the sentence to see what "clicking here" actually does. The second example is self-explanatory.

5. Body Copy

Long copy is good for white-papers and downloadable ebooks, not for your webpages. Short copy with good headlines is a heuristic approach aimed to build trust and confidence. Don't expect users to read your /whitepaper.html page. Most users will see the length and bounce. Use good copy on a short page to build trust, then invite them to download your white-paper or complete an action.

Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.

~ Antoine de Saint-Exupery

Bottom line: if you want to have impact - get to the point – then get out of the way!