iv created a form and have used javascript behaviours to detect when the fields are correctly filled out. they work but is there any way of customising the message which appears in the pop up box when a field is not filled properly?

Uh, we'd need to see the code... we can't suggest modifications to a script we can't see.

The code would help. I'm guessing though since you mentioned a popup message that the code is using the alert() method. You should be able to change the messages there.

heres the code:

<input type="submit" name="Submit" value="Apply" onClick="MM_validateForm('name','','R','phone','', 'RisNum','email','','RisEmail','address','','R','a mount','','RisNum','purpose','','R');return document.MM_returnValue">

would the script fit in among this/before/after?
im pretty new to this and dont fully understand how it works.

the validation function wont validate for radio buttons,just the text fields.when a certian radio button has been selected and then the submit button is clicked i want the pop up to tell the user they cant go any further if its the wrong one.

You would have to find and modify the MM_validateForm function, find where the alert() is and modify the string in there.

Like fundaddu mentioned the code that you would need to modify will be located in the MM_validateForm function. It's mostly like near the top of the page and should start with:

function MM_validateForm(){

or something very similar. There may be some stuff in between the parenthesis. Look for places where the alert() code appears. There will be text inside the parenthesis there as well which should be the text you see in the popup windows.

Feel free to post the code here and we can help. If the page is online posting the link to it will probably be enough.