If you have a web site then you must learn, at the minimum, how to make simple changes and upload the changes. (There is one exception to this).
Even if your site has been designed by a professional there is always going to be a need for some change. Do you want to pay for, and wait for, a designer to do a simple alteration which could take you minutes ?
So you will need to learn the basics of HTML. You can pick up a good understanding by studying the code of existing sites and there are numerous resources on the Net.
You may find however some of this too technical, ideally you want to learn from the angle of setting up a business site.
Fortunately there is an ideal book specifically written for marketers which will show you how to create your First Business Web Site In 10 Days. Click here.
If you then want to start adding a miscellany of special effects to your site, take a look at another book by the same author – 65 Instant Web Design Answers. Examples of some of the tips
How to create a table with rounded corners
How to make a graphic act as a button
How to make an automatic deadline for receiving free bonuses