ShrineDesigns has it right -- inline-level elements are like text, whitespace between them is collapsed to a single space, so there is effectively a space between them.
That said, you're worrying about appearance WITHOUT CSS? Uhm. No. See, HTML is for saying what things ARE -- you have a LIST of thumbnails, so semantically it belongs -- in a list (UL). You want to make that list look a certain way, that's CSS job.
... and avoid using the STYLE attribute (and never use the STYLE tag) -- it's sloppy coding and defeats the point of even having CSS.
The easiest way to deal with them would be to float them, but the bottom alignment you are trying to do won't actually work. A negative word-spacing can work in all browsers except the webkit based (chrome/safari). Display:table on the parent can almost work in the majority of modern browsers, but comes with it's own set of problems.
Likewise you don't have the text WITH the items the text is for -- that's just gibberish from a document structure layout. HTML is about document structure and semantic relationships, as there is more to building a website than what happens to be on the screen in front of you in the browser. Screen readers, braille readers, search engines, print, mobile -- your 'for screen' design could mean jack *** or even make it harder for those to make sense of it... so I'd get that text you have below the images into the same container AS each-image. The anchor might be a good target for that.
But... well, I'm going to be frank with you. A perfect 600px width? So what's your plan when it's narrower than that? What's your plan when someone with a 2048pixel wide display complains about the "crappy little stripe" layout? That's not a 'viable for web deployment' concept.
It starts to sound like your client doesn't know enough about the web to be making choices about how things should be on a website, and that you're trying to implement something that to be frank, has no business on a a website in the first place if you care about actually having visitors and the site being useful TO those visitors.
I'm sorry if that sounds harsh, but I figured somebody ought to tell you before you dig yourself too deep to get out.