Hover your mouse over the button without clicking. Look at the bottom corner of your browser to see the actual destination URL. If it looks like a string of random characters or a different domain entirely, do not click .

Your browser may be flooded with pop-ups, or new toolbars might be installed without your permission.

High-quality ad-blockers can often identify and hide these deceptive "overlay" buttons, leaving only the legitimate download link (if one exists).