Importance of HTML 4.01 Transitional Validation

[peterko]

Hi everybody,

I am running my shopping related site http://www.supremedeal.com.
So far I was using affiliate program links which didn't make me any
HTML 4.01 Transitional Validation problems. (I was using W3C Markup
Validation Service to validate webpages)

Now some of those affiliates are switching their code to Javascript and
at this point the webpages cannot pass the above mentioned validation.

If it's so important, I would rather drop those affiliates than risk
with my site.

Could anyone answer if HTML 4.01 Transitional Validation is really
important?
If the answer is YES, then how it can affect the status of the website.
(SE ranking, PR, are there any penalties for that, etc.)

I would very appreciate someone's answer.

Thank you,