Custom 404s

In php

[huwnet]

I am considering making a custom 404 page in PHP saying the page <PAGEURL> cannot be found.....

Will Google and other search engines no it is a 404 or will the index every incorrect page and then punish me for duplicate content?

[FalseDawn]

Search Engines should not hit your 404 page if your internal links are not broken.

If you are bothered, just add
<meta name="robots" content="noindex,nofollow">

to your 404 page.

[huwnet]

Thanks

[DeanC]

Return a 404 header too using PHP's header() function.

[huwnet]

Stupid question but what is the 404 header?