English translation of CF error messages

It seems to me some people donÆt read the error messages, or somehow donÆt understand the already easy to read messages. In this FAQ I will try to help people understand what some of the most common errors mean.

1)Element FOO is undefined in SESSION.
SESSION could be changed to any variable scope such as APPLICATION, VARIABLES, FORM, URL, COOKIE, [QUERYNAME], or CLIENT. It all depends on the scope youÆre variable is in. FOO is simply the name of your variable. This error simply means youÆre trying to use a variable that doesnÆt exist. Coldfusion doesnÆt automatically assign an ôundefinedö or ônullö value to non-defined variables. Some languages do such as JavaScript or ASP-VBScript.
Remedy: You can use <CFPARAM> to create the variable with a default value if it isnÆt defined. You can also use <cfif> with isDefined(ôfooö) to check your variables before trying to use them. This isnÆt the best way to do it but itÆs handy for looking for the existence of a form submit button on the action page.

2) Invalid CFML construct found on line x at column y
This error can be number of reasons. Basically it means you have a syntax error. Most commonly its caused by not closing quotes, parenthesis, hash marks, brackets, and anything else that has an open/close pair. This error is pretty broad so youÆll have to look at the error message that shows below the actual error. For example <cfset>
The error message is:

ColdFusion was looking at the following text
>
The CFML compiler was processing:
a cfset tag beginning on line x, column y.

Click to expand...

The reason for this error is because Coldfusion was looking for a variable name, not the closing of the tag.

3) Attribute validation error for tag CFOUTPUT
This means one of the attributes inside your tag is either invalid, or has an invalid value. <cfoutput query = ômyQueryö> may cause this error if you do not have a query in your code by the name of ômyQueryö. <cfoutput rs = ômyQueryö> this will throw the same error because RS is not an attribute that Coldfusion accepts in the <cfoutput> tag. This error is not confined to CFOUTPUT. Any tag can produce this error if you provide invalid attribute names or values.

I will add more errors as I see TT members not understand how to read them.