A thread (or a topic) is nothing but a collection of posts. Once your problem solved, you need to mark it as [Solved]. Only mods/admin or a user who creates a thread, will have the option of specifying a prefix as [Solved] to the thread title. As a thread creator (user):
- Go to first post.
- Click on Edit
- Click on Go Advance
- You will then see the selected prefix (including [Solved]) where ever the thread title is shown. Select [Solved] from the drop down menu. Click on Save Changes.