How do I create an index.html file?

In what way? Could you be more specific?

Usually you can just save the file as "index.html" and your computer should recognize the file extension.

Well I'm creating my own css and I'm trying to upload it through a zip file. I have the css I need in there but it's asking for 'Template layout data in a file called index.html'

And I have no idea what it's talking about...

Where are you uploading it to? I'm not sure you have to zip a CSS file.

index.html is the default homepage of the website.

I'm importing it:

Custom Theme file format details:

* A zip file named [your theme name].zip
* Template layout data in a file called index.html
* Style information in a file called main_style.css
* All image files associated with your theme
* All files must be in the root directory or your zip archive. Any files in a subdirectory will not be imported

I have everything made/put together but the index.html file. So how would I put that in the zip file?

I don't really understand what his theme is or what it's for so it's kind of hard to say.

But the index.html file is the homepage of a website, and it's where all your HTML and content is placed. Everything from your stylesheet would be put together in the index.html file. You can create it in a text editor like Notepad and then just save it as index.html and put it in the same folder as everything else. I mean, think about it, if you ONLY had a stylesheet, nothing would show up, because you haven't specified anywhere how the elements will be set up.

It's confusing the hell out of me.

I'm using http://www.weebly.com/, I'm trying to create my own home page so I go to Design - Custom - Import and that's what it asks me for.

I created the index.html file in notepad and saved the stuff there and it still won't work.

In Notepad, did you make sure to change the "Save As Type" drop-down menu to "All Files?"

If so, what does it say now? =/

Well, this advise is probably not what you want to hear, but it could just be weebly making a mistake. try going to tool>clear private data and un-checking everything other than the cache. It's what I always do when something's not working that should. No promises, I sometimes just give it a hour or so to work itself out, you never know what'll work.

If you have an external stylesheet it's not going to show up even if you just create an index.html file, I think you have to call it from your index.html file- although I have no clue how weebly works so maybe you don't need that?

I'm not sure what exactly Weebly is, but If you doing coding for a website by hand, you use this code to get the external stylesheet to format the page you want it to:

<link src="myFile.css" type="text/css" rel="stylesheet" />

I"m only in my second semester of web design, but I hope this helps ^_^

EDIT: If that works, you might also want to try the W3C website for help