when i had open home page and started surfing my website, some another websites opening automatically,and it repeat again and again last 15-20 days.

What are in these other pages? Ads? You may have ad / mal-ware. Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.