If your friend is sensible enough he wouldn’t send you links with questionable content with a NSFW warning. But what if he didn’t and you are unsure whether to open it or not? Or what if he did but now you are tempted to take a peek while at work?
If you find yourself in such a quandary, got to Variably Safe For Work and paste the URL of the questionable link and click the Preview button. The application will load the page but will prevent it from being seen by overlaying an opaque screen on top of it. Slowly drag the slider at the top to gradually reduce the opacity of the black overlay screen. The website will fade into view enough for you to judge what the content is about.
Once you are sure the site is safe, click on the Proceed button to open the page normally.
Unless they proxy the data and images from the potentially unsafe site, your browser will download html and images from the unsafe site, and the network people will see your http footprints. Good luck explaining that the screen was opaque.