I am new to SPFx, tried to create simple webpart using SPFx. Referred from here.
Followed these steps:
-Installed nodejs
-Installed gulp & yomen using npm install -g yo gulp in powershell.
-Loaded sharepoint framework using npm install -g @microsoft/generator-sharepoint
-Now created a new directory using md helloworldspfx
-Navigated to the directory cd helloworldspfx
-Tried to create the webpart using yo @microsoft/sharepoint
-Installed developer certificate gulp trust-dev-cert
-Tried to build & preview the webpart using gulp serve
Now workbench page opens up in chrome like this, 
There is no error showing in the windows powershell.
Please help.
SOLUTION:
I have been using Node.js v8.9.
With the help of answer setting the NODE_NO_HTTP2=1 environment variable to disable the experimental feature.
Like this, $env:NODE_NO_HTTP2="1" in powershell (set NODE_NO_HTTP2=1 in CMD) to fix the issue.