Viruse problem

Hello,
i am using nokia 3110 classic mobile for internet access and sometimes i have to download some files then after that my mobile became hang and music player doesnot start. in first it start as saying uploadin music files but when the process is complete it says the music files are not found. so i want to know how to protect my cell phone from viruses while using the internet. does only using the yahoo messenger and facebook can allow the viruses to enter my phone? please tell me how to secure my phone from viruses while using the internet