What's this in my lawn... and how do I get rid of it?!

Hello!

I've been watching this stuff appear and grow amongst the grass, and I'm finding it difficult to get rid of. It doesn't seem to respond to lawn weed killer or weed and feed. Does anyone know what it is and how to kill it without killing the surrounding grass by going straight for the regular weedkiller?

its like ground cover clover, multiple tiny cactus-like leaves. I've tried to search for it in weed indexes but can't find anything similar. The grass seems to give up when it appears.

Thanks

 

Look up liverwort. Caused by poor drainage and low light.
You don’t need a weed killer for that, you need to improve the area for the grass plant.