If you're doing more than a simple search on Google, you probably want those links to open in a new tab instead of the current one so that your original results are always available. Here's how to make Google open your results in a new tab every time.
If you'd rather have Google not open your results on the same page, you can set the default by going to Google and clicking on the cog in the upper right-hand corner. Choose "Search Settings" from the list, then scroll down to "Where Results Open". Check the box for opening them in a new tab, press Save, and you're good to go — Google will never cover up your results list again. Hit the link to read more, or to see another, more Firefox-centric method for doing the same thing.
How to Have Google Always Open Search Results in a New Tab [Guiding Tech]