.htm and .html ¦ + and - in urls

need some clarification about having these in url

[pxhost]

I'm very new to the SEO world. I simply want to know if google likes + signs in urls, does it treat those the same as - do? Everyone always goes off on a tangent how underscores combine the keywords and blah blah, thats great. I understand that. But what about the plus sign? Does that have the same effect/result as -? Has anyone performed tests with this?

My second question about the .htm and .html. I know they are both the same thing. Is it ok to have a site that has both of them though? Using mod_rewrite, i was contemplating the possibility of determining what page to load based on the extension. If it's .htm, it is more than likely a content page. If it's .html, it should treat is as a url for a shopping cart, or whatever app.

Any suggestions? Reason why i care about the + sign, is because if indeed it IS a good thing, or makes no difference with the -, it would make it easier to reverse engineer my url's just in case a category name has a hyphen in it. At the moment i am replacing - with spaces and vice versa.

Any help is greatly appreciated. Thanks.

[Quadrille]

If + ¦ work ok, then Google will allow them - but from an SEO POV, they certainly won't help, and could conceivably hinder.

Much better to stick to things that are proven - the fact that + has not surfaced in 10 years is probably a clue ;)

Never use spaces in filenames or folders - it will appear as %20 - not pretty, and certainly not useful.

Suffixes do not matter matter to SEs (so long as they work).

[bill]

...or eliminate the file name altogether. Look into cruft-free URLs [google.com].

[g1smd]

The + is OK.

Google uses them in multiple-word search query URLs.