Because of Mozilla’s compliance with W3C-CSS, entities, CSS, and style-attributes require units when measurements are expressed. Hence, “font-size:4.1898;” is invalid syntax. To ensure proper rendering, first add “px” to all font-sizes in order to get strings like “font-size:4.1898px;”. The second possibilty is to export with “presentation attributes” as in attribute-style writing (XML) –no uni are needed as long as they are expressed in the main coordinate system, but this results in larger files.

Use these Save a Copy settings:
DTD: 1.1
Text: SVG
Subsetting: none (system fonts)
DO NOT Preserve Illustrator Editing Capabilities
CSS: Style Elements (generates a set of 25 style definitions in the file header) –> make sure to add px units
3 decimal places
UTF-8
Uncheck: Optimize for ASV, Include Adobe Graphics Server data, Include Slicing Data, and Include XMP
Check: Output fewer <tspan> elements and Use <textPath> elements.