There are distinct advantages to opening a customized start page in every new tab you open in your web browser. Most modern browsers come with a tiled list of thumbnails to give you access to your most frequently visited sites. The potential problem with this approach is that these personalized pages can often lead to random web browsing. If you visit, say, Facebook often, you may open a new tab with the intent of going to a specific page, only to be reminded that you haven't visited Facebook in the past hour... and now Facebook (and all its distractions) is only one click away.
To streamline your web browsing, try setting your new tabs to redirect to a page that forces you to make a conscious decision as to where in the world wide web you'd like to go. If you use Chrome, you can use this extension to specify exactly which page will open in new tabs. This Firefox extension will do the same thing. (Note: by default, Firefox opens a blank new tab, which is perfect for our purpose, but a bit too bleak). Although I'm not extremely familiar with Safari, I'm sure a bit of Googling will help you find a similar extension. I'm unaware of any such capability for Internet Explorer (which you shouldn't be using, anyway).
Here are a couple of my favorite pages to use in a new tab:
It doesn't get any more minimal than this. You are presented with one search box (powered by yubnub) and nothing else.
Helvetictoc is my new tab page of choice. It's a simple clock, presented in real language, that pays homage to the most popular and timeless of fonts: Helvetica. During daytime hours, it's presented as black text on a white background. During nighttime hours, the colors are inverted. There are no search boxes, so again you must make a conscious decision as to what website is worthy of your attention at a given moment. By subtly reminding you of the time, you can also be aware of how much time was spent doing whatever task you were previously attending to in your last tab.
By eliminating the visual reminder of your most-visited or favorite sites with the opening of every new tab, you eliminate the possibility of random web browsing, which means your online journey becomes a much more deliberate and conscious one. Try it for a few days, if just to remind yourself how unconscious your web browsing habits have become.