Last semester I was asked to design a website required by my web teacher. Since I had no experience and basic knowledge in web designing, I had no choice but to download some exemplary codes to learn how to satisfy the teacher’ requirement. However, in most cases, not all parts of the codes are perfect. It is no exception that the codes I copied from the website have a few bugs and the effect was not the same as it was demonstrated on the web page. To tackle these problems, I read some books and understood the principle. Finally, I found that the code pasted on the web page was not complete. The author missed some codes that he believed the coders equipped with basic knowledge could know, but before learning the principle, devoid of the fundamental background knowledge I didn't know how to supplement the missing codes. Since the name of the variable in .js document didn't match the name of the same variable in the web.xml and some necessary variables were not declared in web.xml, the picture cannot be uploaded. Although this is a subtle problem, it confused me for a few hours. Therefore, before I begin to code, it is better for me to learn the basic knowledge which could equip me with the ability to address the problems I encounter next time.