How to make a div fill the remaining horizontal space?

Dig deeper, knight of code!

While the fast answer is your save-the-day hero, circumstances might call you to wear different caps. Supporting legacy browsers or handling advanced layouts demand more weapons in your armory. Let's sharpen those weapons!

Floats and margins: good old-fashioned charm

Before Flexbox, floats were the MVPs for layout position. Team them up with margin to fill up that remaining space:

.left-div {
    float: left; /* Float like a butterfly 🦋 */
    width: 100px; /* But sting with a fixed width */
}

.right-div {
    margin-left: 100px; /* Right div grudgingly admits left div's size */
}


Overflow: unleash the beast

Let's talk about the elephant in the room: overflow when you're dealing with floats. The overflow property commands a new Block Formatting Context (BFC) - and the div gracefully expands whilst neatly sidestepping those floated elements:

.right-div {
    overflow: auto; /* BFC's magic trick 🎩🐇 */
    margin-left: 100px;
}


Display table: pick up the ancient relic!

For a nostalgic stroll through older browser support, pickup 'display: table;' and pass on 'display: table-cell;' to its descendants. You will end up with something that might smell like Flexbox, but with a vintage aroma:

.table-container {
    display: table;
    width: 100%; /* As wide as the horizon 🌅 */
}

.left-cell {
    display: table-cell;
    width: 100px;
}

.right-cell {
    display: table-cell; /* Flexible like a gymnast 🤸‍♂️ */
}


For an epic showdown with the dragon called "IE", arm the .right-cell with a shield called "auto".

Embrace cross-browser compatibility. In Flexbox we trust, but deliver we must on all platforms.

Comparing Flexbox and Traditional Floats

When Flexbox is your knight in shining armor:

• Independence: Flex items can stand tall without leaning on their comrades.
• Adaptiveness: Adaptive screen sizes? Flex items got your back.
• Synced: Unvarying across different realms (ahem, browsers).

However, the brave old soldier, Floats, still holds the fort:

• Legacy Support: Compatibility with old browsers? Floats have seen it all.
• Simplicity: Straightforward layouts need straightforward methods.
• Familiarity: For those who whizz through traditional CSS layout techniques.

The Grid of Troubles and how to conquer them!

In your heroic jedi-coding journey, you may encounter usual foes:

• Fight of the Styles: Beware of existing CSS commands trying to pull your layout strings.
• Case of the Overflow: Employ overflow: hidden or overflow: auto to keep unexpected rebels at bay.
• Mixed Potion Dangers: Stick to one potion (px, rem, etc.) for foreseeable results.

Never forget, your faithful sidekicks, Chrome DevTools, or Firefox Inspector, are always there to help analyze and conquer battles effectively.