First time website builder, so I'm still a bit shaky on how exactly CSS applies to html docs.
I'm trying to split my page into 2 divs, each taking 50%. The left contains an image, whereas the right contains text. This forms a side-by-side configuration.
When I enter my code as such:
<div class="infobox">
    <div style="float:left;width:50%;">
        <img src="foo.jpg" style="max-width:95%;height:auto;margin-top:10%;border-radius:10%;overflow:hidden;" alt="">
    </div>
    <div style="margin-left:51%;">
        <h1>MAIN PAGE</h1>
        <p>Welcome to the page. This is a test message for the time being. This will eventually become
                    replaced by full text.</p>
        <p>Welcome to the page. This is a test message for the time being. This will eventually become
                    replaced by full text.</p>
        <p>Welcome to the page. This is a test message for the time being. This will eventually become
                    replaced by full text.</p>
        <p>Welcome to the page. This is a test message for the time being. This will eventually become
                    replaced by full text.</p>
        <p>Welcome to the page. This is a test message for the time being. This will eventually become
                    replaced by full text.</p>
    </div>
</div>
everything works as expected. The image stays in its div, has rounded borders, etc.
However, when I try to move the css code to my master.css file, everything breaks. My code is as follows:
<div class="infobox">
            <div style="float:left;width:50%;">
                <img class="image-style" src="foo.jpg" alt="">
            </div>
            <div style="margin-left:51%;">
                <h1>MAIN PAGE</h1>
                <p>Welcome to the page. This is a test message for the time being. This will eventually become
                replaced by full text.</p>
                <p>Welcome to the page. This is a test message for the time being. This will eventually become
                replaced by full text.</p>
                <p>Welcome to the page. This is a test message for the time being. This will eventually become
                replaced by full text.</p>
                <p>Welcome to the page. This is a test message for the time being. This will eventually become
                replaced by full text.</p>
                <p>Welcome to the page. This is a test message for the time being. This will eventually become
                replaced by full text.</p>
            </div>
        </div>
And in my master.css file:
.image-style {
    max-width: 95%;
    height: auto;
    margin-top: 10%;
    margin-left: 10%;
    border-radius: 10%;
    overflow: hidden;
}
When this second method is used, side-by-side configuration breaks. The image now takes up 100% of the screen, with the text still in the correct position above it. Additionally, none of my style changes apply to the image. I don't understand; doesn't the image inherit it's size/positioning restrictions from the div it's inside of? Why isn't it inheriting the div above it in this format, and why isn't the image accepting the class style?
I feel like I'm missing something completely obvious, but I just can't see it anywhere. Any assistance will be greatly appreciated.
 
     
    