1. Yesterday i was working on my page, DW working fine and showing tag outline.
2. An today DW not showing tag outlines. pls help me ASAP.
Please share the test file with us to find the right issue and help you out.
Make sure that Visual Aids haven't been turned off. View > Visual Aids
You've probably turned off all visual aids accidentally by pressing Ctrl+Shift+I/Cmd+Shift+I.
If that's not the case, make sure there's a check mark alongside CSS Layout Outlines.