Update: The following was written for Android 2.x and is not in-line with Android 4.x and above. In latest Android, you have to look for "Application manager" in Settings (location differs from phone to phone), and clear cache/data for all your browsers (Internet, Chrome, Firefox, etc). Again be sure to backup your stuff or use some form of sync (like Google sign-in on Chrome or Firefox Sync) to save them.
If your android browser has been hijacked and you find your home page and default home page have been changed to www.searchmobileonline.com, follow the procedure to get rid of it.
Warning: Backup your browser bookmarks using a good app before you do this! All bookmarks will be lost from the Internet browser, including those that came pre-installed on your phone.
1. Remove any suspicious "Search" shortcut on your home screen panels.
2. Open Settings > Applications > Manage applications > All (tab on top).
3. Look for "Internet" in the list and open it.
4. Tap "Clear cache" (if enabled) and "Clear data".
5. Tap OK to any prompts that appear.
That's it, now you can exit out of Settings and open Internet. Check the settings if the default home page now points to either Google or your phone manufacturer. Set the various internet settings according to your preferences and restore the bookmarks you backed up.