Find and replace string

[c a g a t a y]

I wanna find an unregular string like;

<script type="text/javascript" src="………. </script>

and change it;

<null>

How can I
Any idea?

Regards

[c a g a t a y]

<script type="text/javascript" src="xxxxxx </script>

xxxx changes in every file

[Me & Myself]

you can try this:
<script.*</script>
for complex scripts you can try to set "dot matches newline"

[c a g a t a y]

Nothing found