SVG can do this nicely using patterns:
<svg width="100%" height="100%" xmlns="http://www.w3.org/2000/svg">
<defs>
<pattern id="smallGrid" width="8" height="8" patternUnits="userSpaceOnUse">
<path d="M 8 0 L 0 0 0 8" fill="none" stroke="gray" stroke-width="0.5"/>
</pattern>
<pattern id="grid" width="80" height="80" patternUnits="userSpaceOnUse">
<rect width="80" height="80" fill="url(#smallGrid)"/>
<path d="M 80 0 L 0 0 0 80" fill="none" stroke="gray" stroke-width="1"/>
</pattern>
</defs>
<rect width="100%" height="100%" fill="url(#grid)" />
</svg> I set width and height to 100%, so you can define the actual width and height on use, either for inline SVG:
<div style="width:400px;height:300px">
<svg width="100%" height="100%" xmlns="http://www.w3.org/2000/svg">
<defs>
<pattern id="smallGrid" width="8" height="8" patternUnits="userSpaceOnUse">
<path d="M 8 0 L 0 0 0 8" fill="none" stroke="gray" stroke-width="0.5"/>
</pattern>
<pattern id="grid" width="80" height="80" patternUnits="userSpaceOnUse">
<rect width="80" height="80" fill="url(#smallGrid)"/>
<path d="M 80 0 L 0 0 0 80" fill="none" stroke="gray" stroke-width="1"/>
</pattern>
</defs>
<rect width="100%" height="100%" fill="url(#grid)" />
</svg>
</div> or an <img> element:
<img src="https://svgshare.com/i/eGa.svg" width="700" height="200"/>
results in:
(Sorry if the image does not show up – there does not seem to be something like Imgur for reliably hosting SVGs.)
<img src="https://svgshare.com/i/eGa.svg" width="241" height="401"/>
results in
Note that for this particular grid you have to use widths and heights of the form n x 80 + 1 (with n being any integer) if you want the grid to start and end with a thick stroke.
