If I have this style:

div.InformationTitle
{
   font-size: 16px;
   color: #000000;
   font-weight: bold;
   text-transform: uppercase;
   font-style: normal;
}

div.Content
{
   font-family: Calibri, Arial, Helvetica, sans-serif;
   font-size: 14px;
   font-style: normal;
   font-weight: normal;
}

And, this code:

<div class="Content">Articles about something <b>Internet Applications with <i>Visual FoxPro 6.0</div><div class="InformationTitle">Speaking experience</div>

...this will having the "Speaking experience" text to be italic.

However, if I insert a space between the two divs:

<div class="Content">Articles about something <b>Internet Applications with <i>Visual FoxPro 6.0</div> <div class="InformationTitle">Speaking experience</div>

...then, the "Speaking experience" text is not italic.

On the second example, the style InformationTitle properly reads its CSS definition. The CSS definition tells that style to have a font-style normal.

Why is this not working on the first example and why the space is a factor?

Basically, as the style includes a font-style normal, I would expect the font-style to always be normal no matter is an italic tag has not been properly closed above.