There are beginning to be a large number of tools available for creating RSS feeds from scratch. Since RSS is a very specific file format, it is important that your RSS feed tools follow specification, else some directories may not list your feed and even worse, some users may not be able to view it.
While many of the RSS tools out there create perfectly compliant RSS feeds, others may use old rules and create an RSS feed which contains out-dated fields or even errors. This is true for both RSS and ATOM feeds.
You might have discovered the free RSS service FeedValidator, which lets you know if anything is wrong with your feed. But it can return some pretty confusing errors if anything is off.
Since RSS Submit includes a validation feature to help you check your feeds prior to submission, this is a key topic to elaborate on.
So the question arises, how important is it that your feed is 100% compliant?
Well, in all honesty, it really depends if you're a type A or type B personality. Us? Take a look.
Keep in mind that FeedValidator will check your feed against every single rule in the specification. If your feed passes, you can rest assured you are 100% compliant. However, not all RSS directories and feed readers need this. In fact, many will still display your feed just fine if it is only a matter of a few errors being returned.
Some example minor errors:
"item should contain a guid element"
Explanation: "It's recommended that you provide the guid, and if possible make it a permalink." However, this is a rather new field and optional. Most, if not all, directories and readers will accept your feed without the guid field.
"width must be less than X in size"
Explanation: "The image width must be less than size X" This is another field which is usually ignored by most readers.
"This feed uses an obsolete namespace"
Explanation: "This feed is using an obsolete namespace used by an obsolete snapshot of Atom, which is not supported by this validator." But the feed may be perfectly fine for the directories and readers, still this will show as an error in the validator.
"Unexpected version attribute on feed element "
Explanation: "Your feed contains elements with attributes that are not defined in the relevant specifications" However, the directories and readers may simply ignore this field.
"Unexpected mode attribute on title element"
Explanation: "Your feed contains elements with attributes that are not defined in the relevant specifications. " Again, this will likely be ignored by feed readers.
If your feed is showing some erros, but you insist it's a valid feed, you may want to read the full details on what FeedValidator considers an error and a warning.
What if you don't want to bother fiddling in XML and correcting the errors by hand?
One solution would be to use a different tool to create your feed - a tool which hopefully follows the standards better. For example, FeedForAll may help.
Another solution would be to send your feed through the free service FeedBurner. Assuming your feed is at least readable, they will provide you with a proxy feed URL, which points to a valid and compliant RSS feed, made from your original. Not to mention, they will also let you record traffic and add extras. But for making a compliant feed, they are also helpful. You would then submit the feed URL they provide to you.
In summary, I would always recommend making sure your feed is 100% compliant by checking it in FeedValidator.org or by clicking the little "Validate" button in RSS Submit. This will ensure maximum acceptance when submitting to the directories. Besides, it gives you a good feeling seeing the glowing message "This is a valid RSS feed!".