What should I do, as I have repented to Allah after I used to curse and utter obscenities on an online chat site, and I am unable to find these people to ask for their forgiveness?

A believer is not one who slanders, curses, or is obscene. If he errs, he must repent to Allah, the Almighty. For one who desires sincere repentance, he must regret past sins, abandon them, resolve never to return to them, and restore injustices to their rightful owners. If the injustice relates to one's honor (backbiting, slander, or cursing), he should contradict himself in front of those with whom he committed the act, and seek forgiveness from the wronged person if possible without causing discord. Otherwise, he should turn to Allah the Almighty to appease Him. He should mention the person he backbit in a good light in the same place and frequently supplicate for him and seek forgiveness for him in secret.

To strengthen faith and steadfastness, it is recommended to read books on encouragement and discouragement ( الترغيب والترهيب), books on softening the heart (الرقائق), ponder the Quran, reflect on the afterlife, be mindful of Allah, keep company with the righteous, increase supplication, and avoid bad companions.