If your site is based on PHP, the most likely cause of the problem is that you missed a symbol somewhere. Just skipping 'or} or; somewhere in the code, your code won't work. You will not receive an error, you will see a blank page.
1. PHP Error Reporting. You can find out a lot about what went wrong from the error message that PHP provides. If you do not receive an error message, you can use the instruction to configure error output: http://php.about.com/od/troubleshooting/qt/php_error_reporting.htm
2. Test your code more often. If you check each piece of code after adding it, then at least you will know where to look for a problem if it arises.
3. Use a text editor with code highlighting. Most editors allow you to visually identify problems in the case when you missed a sign, or made a mistake in writing expressions.
4. Comment out some of the code to isolate the problem. Start at the top by commenting out a few lines and then insert echo () with a test message just below the comment. If echo () works, then the problem is below. Comment out the following piece of code and place echo () below it. In this way, you can check all the code until you identify the problem.
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