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I need to know what this Error(1): &quot;<a href="http://java.sun.com/jstl/core" rel="ugc">http://java.sun.com/jstl/core</a>&quot;&nbsp;is not a registered TLD namespace mean.<br />
I am using JDeveloper, want to create a calendar button. <br />
Thank you.
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I need to know what this Error(1): "http://java.sun.com/jstl/core" is not a registered TLD namespace mean.
I am using JDeveloper, want to create a calendar button. 
Thank you.

what is the error message mean?

JavaServer Pages (JSP) allow the development of dynamically generated web pages. It uses the Java programming language; JSP pages are translated into servlets at runtime, with each servlet being cached and reused until the JSP is modified. JSP allows Java code to be interleaved with static web markup content, so the resulting page can be compiled and executed on the server to deliver the content.

Software is any set of instructions that directs a computer to perform specific tasks or operations. Computer software consists of programs, libraries and related non-executable data (such as documentation). Computer software is non-tangible, contrasted with computer hardware, which is the physical component of computers. Software written in a machine language is known as "machine code". However, in practice, software is usually written in high-level programming languages than machine language. High-level languages are translated into machine language using a compiler or interpreter or a combination of the two.