WordPress warning: Cannot modify header information – headers already sent

Problem: I keep getting the “Cannot modify header information – headers already sent by myfile.php in pluggable.php in WordPress 2.8.3. It prevents my pages from loading. What should I do? It is urgent… Anything outside the
 <?php ... ?>
tags in a PHP document is written to the response body. There is something before the very first line of your myfile.php. You have probably saved your source file as UTF-8 with a byte order mark (BOM) and your declared encoding is something like ISO 8859-1. Remove the leading 3 bytes of “EF BB BF” from your source file with a binary editor. For example the Visual Studio has a well hidden editor: File -> Open File -> choose your file -> click on the Open button’s selection bar -> Open With -> Select binary editor -> Open.