Since every site is coded differently... without giving more info you will never get a useful answer.

Do you have a sample codes of that project that you're trying to do? Cause I can't help cause' I don't really know what you're trying to see on your output and even what you're using is it php,html or what? but this site help you..W3Schools Online Web Tutorials all you need to know is there

In general there are 2 ways to do it:

1) By abbreviating the page name or removing extra words. If you are using WordPress, some themes (ClickBump, Thesis, etc) have a "Custom Post Title" field that makes this easy. For example, you can have a smaller, "menu-friendly" Page Name, and then expand on this with a more descriptive, keyword-rich "Custom Post Title" that shows up in your actual <title> tag and atop your post content.

2) By using custom css to adjust the padding and margins between your menu elements. If you will post a URL to your page where the menu can be seen, I can give you a specific CSS code to use.

Let's see your site so we know what you're talking about...

What is the actual width of your website? is your navigation menu characters breaking the theme structure?