Text to appear on hover of image

How can I display a block/text when a user hovers or clicks on an image?

I found a few good posts. Here and Here

I also found external sources. Each place I went provided a solution similar to this:

http://jsfiddle.net/p87g3fey/

Follow the link above to see it in action

HTML

<a id="thumbnail" href="#">
<img src="http://dummyimage.com/150x150/0066ff/fff"></a>
<div id="title">filename.jpg</div>

CSS

#thumbnail {
display: block;
width: 150px;
height: 150px;
}

#thumbnail:hover + #title {
display: block;
}

#title {
display: none;
color: #ffffff;
background-color: #000000;
text-align: center;
width: 130px;
padding: 10px;
}

I don't understand what I'm doing wrong in my code though. Here's what I have:

HTML

<div class="sqs-block image-block sqs-block-image" data-block-type="5" 
id="block-yui_3_17_2_2_1428673541254_6455"> </div>

<div class="sqs-block html-block sqs-block-html" data-block-type="2" 
id="block-yui_3_17_2_3_1429198468651_10272"><div class="sqs-block-content">
<p>I want this text to appear when the calendar image is hovered (and 
preferably clicked too)</p></div>

CSS

#block-yui_3_17_2_2_1428673541254_6455 {
display: block !important;
}

#block-yui_3_17_2_2_1428673541254_6455:hover + 
#block-yui_3_17_2_3_1429198468651_10272 {
display: block !important;
}

#block-yui_3_17_2_3_1429198468651_10272 {
display: none;
color: #ffffff;
background-color: #000000;
text-align: center;
width: 130px;
padding: 10px;
}

I literally just swapped out the selectors to match what I want done: When a user hovers over the calendar image on the right, I'd like text to appear on the left. I've tried other solutions, similar to this with no luck. Any ideas where I'm going wrong? Reason I'm selecting block-yui is that they indeed are static and work: https://answers.squarespace.com/questions/76450/how-to-select-just-1-image-on-a-page

The page I'm working on is here: http://www.p2sk.ca/testing-grounds

Some pretty good designs here and here

It seems to be working now, albeit with bad formatting.

Out of curiosity, why is it bad code?