mcfly gave a great overview. HTML5, plus CSS3, plus JavaScript and my favorite too jQuery...yeah, it feels so good that so many headaches have gone away. The new browser tech has enabled a lot of good design tools, too, many of which run in a browser, or wrap a browser (Microsoft Visual Studio has a free edition like that).

mcfly's post also screamed "Windows!" when he talked about the server, and I think it's because he's worked in corporate shops. The "enterprisey" stuff (though rarely starships). The Windows world has the powerful advantage of familiarity, but Windows web servers are more expensive to set up and operate compared to Linux (there, he dropped the gauntlet!...though I admit that long ago, I was the Windows guy manning the ramparts against Linux...we learn, we grow).

If you run your own hardware, you'll pay those huge Microsoft taxes, versus free for Linux, Apache, MySQL, and PHP. But I don't recommend running your own hardware anymore, go cloud, my man, go cloud. Clouds commodify things, but there you still see a Microsoft tax of about 33% (https://aws.amazon.com/ec2/pricing/on-demand/). You can run a small, "brochure-ware" web site at Amazon for around $50/month (base Linux). I'll come back to Linux in a second.

As for your database, just say no, never, absolutely not, to Access. It's a single-user office desktop consumer product that breaks with two or more concurrent users...you know, like a web site. Microsoft's SQL Server you can get in a free developer's edition, aka "desktop" edition, which is a red flag. Huge licensing fees for server grade SQL Server; and in the cloud, the cost of a Windows server goes from about 20 cents/hour to about 67 cents/hour if it includes standard-edition SQL Server (the base hourly is higher than what I was using before, because adding the DB requires bigger hardware [the base 20c/hour]; the extra 47 cents is just adding the SQL server license).

Whether you run Windows or Linux, you can install open source mySQL server, or a close-clone "Maria". Some people prefer Maria on the principle that Oracle bought mySQL Server a few years back, and they're evil, so there. Both are free. You'll need a DB one way or another, at a minimum for login credentials, but more likely to hold content in a CMS:

It's almost never necessary to build a Web site from scratch any more. There are a lot of "Content Management Systems" around (CMS) that install a turnkey web site that you customize and fill with content through a web interface. The content is stored in a database, and there are very few actual HTML pages, just master templates for page designs, filled from the DB.

I recommend the venerable WordPress, currently running about 75 million web sites. Disclosure: I'm trying to make money building WordPress plugins. Not that my personal recommendation is going to cause the slightest flutter of a ripple of a twinge in their stats, but still...

A lot of people know WordPress. TB, for example. You've no shortage of help and advice. And the market for add-ons is impressive, much of it required to be free by the terms of WordPress's license. There are themes to customize the visual appearance, add-ons that add behind-the-scenes functionality, like membership management. WordPress is associated with blogs, but a blog is only one possible configuration--WP's a general-purpose web-site machine. Themes turn it into other things, including company portals and collaboration tools. See wordpress.org/themes to get a feel for the range. I've seen themes very close to what you describe: Simple marketing material facing the public, private material and services like a calendar, HR forms, etc, behind login. WP will take care of a lot of the SEO, and for heavy-lifting there are plugins for that.

Back to Linux. It has a reputation for being a lot harder to work with than Windows, and that's partially justified. Linux isn't dependent on a GUI for administration (though you can get GUIs even for servers), and hard-core geeks use a command-line terminal. I fry eggs with my bare hands, too. But though Windows has an extensive administration GUI for servers, the advantage is somewhat mitigated by the fact that if your server is remote, you have to login with remote desktop sharing software, or use a terminal just like the grownups. Meow.

There are remote (web) administration packages that work on either OS. Webmin(.com) is a popular one. A good set of control panels levels the playing dramatically--from a distance it's a generic server, with boring generic forms to change generic settings.

I would also recommend WordPress because you might have fun with it. It almost always installs painlessly, you can play with it to your heart's content before commiting; or throw it away and try something else, at little cost. But you might enjoy plugging in free add-ons and playing with the customziation to build up a web site. Adding content is painless with WYSIWYG editors.

I recommend the cloud for the same reason. Building and being responsible for real hardware can be fun at first, but gets old fast. In the cloud the staff does the grunt work of keeping everything running, and you get to play with a virtual data center Lego set, commissioning servers and database and gateways and all the virtual toys, all by clicking on forms. The power!

Second also to mcfly's advice about making sure you're given time enough to work on this without undue pressure. Your company will be rewarded if they let you approach it calmly and deliberately, and in the spirit of having a good time with it. Happy web developers make happy web sites.

And I hope you do have a good time with it. We're all here if you need us, remember that!