
By Default Blogger shows Error page message in a box and its not look Style.
Here I am saying about how to Customize it much better...
Only Custom message [No Style]
If you want to show only a custom message then First Go to updated Blogger InterfaceThen Go to Setting->Search Preferences

Error Message with Stylish 404 images
If you want Colorful Stylish 404 page do the following.- Go to Design->Edit HTML
- Find </head> and copy the below code just above it.
<b:if cond='data:blog.pageType == "error_page"'>
<style type="text/css">.status-msg-wrap{font-size:100%;margin:none;position:static;width:100%}.status-msg-border{display:none}.status-msg-body{padding:none;position:static;text-align:inherit;width:100%;z-index:auto}.status-msg-wrap a{padding:none;text-decoration:inherit}</style>
</b:if>
<style type="text/css">.status-msg-wrap{font-size:100%;margin:none;position:static;width:100%}.status-msg-border{display:none}.status-msg-body{padding:none;position:static;text-align:inherit;width:100%;z-index:auto}.status-msg-wrap a{padding:none;text-decoration:inherit}</style>
</b:if>
- Save the Template
Error Page Style 1

- Go to Setting->Search Preferences
- Copy below code in Custom Page Not Found section [as shown in fig. first]
<h2 style="font-size: 35px;margin: 0;text-align: center;">Oops..! </h2>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibZ8TPmaLxhOKMC30d9nTbZTurVfg6NPs272w-UxosK-WSlCIxxRR1abz5Rr16xjvxXX1Oso8vVJ-aQo7RkxtBLMD7q7ryk5WPr0o4XFVME7IePfVbgzWKKdsZkmlufvgCly_l_uTwHhw/s1600/404+error+page+1.jpg"/>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibZ8TPmaLxhOKMC30d9nTbZTurVfg6NPs272w-UxosK-WSlCIxxRR1abz5Rr16xjvxXX1Oso8vVJ-aQo7RkxtBLMD7q7ryk5WPr0o4XFVME7IePfVbgzWKKdsZkmlufvgCly_l_uTwHhw/s1600/404+error+page+1.jpg"/>
Error Page Style 2

- Go to Setting->Search Preferences
- Copy below code in Custom Page Not Found section [as shown in fig. first]
<h2 style="font-size: 35px;margin: 0;text-align: center;">Oops..! </h2>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI398Ux8fMbygnj3xd-vcaGoEj5D3KiSk-qDt1tdizinkO9pJUkeU3r2_6WgUdeqySMhuOoopnQmT9KKh2vgvIkdJA6wBMzwoq4Y3xYgS4gu7ZL1a4cftva3gptBBczTvW2sFJmhBV2gc/s1600/404+error+page+2.jpg"/>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI398Ux8fMbygnj3xd-vcaGoEj5D3KiSk-qDt1tdizinkO9pJUkeU3r2_6WgUdeqySMhuOoopnQmT9KKh2vgvIkdJA6wBMzwoq4Y3xYgS4gu7ZL1a4cftva3gptBBczTvW2sFJmhBV2gc/s1600/404+error+page+2.jpg"/>
Error Page Style 3

- Go to Setting->Search Preferences
- Copy below code in Custom Page Not Found section [as shown in fig. first]
<h2 style="font-size: 35px;margin: 0;text-align: center;">Oops..! </h2>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFsasPUeXjL5iXMthYJ5fUHUTYodj1_aUwyMyKXF-giw4WIN5_sa-oex4kWHmKJxyBoPv7jIGwp9PwIJODy42q13J8wU0kSJhKYBMwsDQQYtvwVK7-1T6Af_Q6ypGLk_YmwAkdJc8m0dw/s1600/404+error+page+4.jpg"/>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFsasPUeXjL5iXMthYJ5fUHUTYodj1_aUwyMyKXF-giw4WIN5_sa-oex4kWHmKJxyBoPv7jIGwp9PwIJODy42q13J8wU0kSJhKYBMwsDQQYtvwVK7-1T6Af_Q6ypGLk_YmwAkdJc8m0dw/s1600/404+error+page+4.jpg"/>
Error Page Style 4

- Go to Setting->Search Preferences
- Copy below code in Custom Page Not Found section [as shown in fig. first]
<h2 style="font-size: 35px;margin: 0;text-align: center;">Oops..! </h2>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwcmnBl1SWqnmnXQQxGLHASix93YsRd_pRAaiDCuaaaYw1M6YRjhWmMxRJmcardqSlWrnkSu_W2wcII84G01dC-bO3uw6ZxEdbPPaE4m9TukZ6zNS2YA_CrLd4UVs1-_j4mzfLvMAV2uo/s320/404+error+page+6.jpg"/>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwcmnBl1SWqnmnXQQxGLHASix93YsRd_pRAaiDCuaaaYw1M6YRjhWmMxRJmcardqSlWrnkSu_W2wcII84G01dC-bO3uw6ZxEdbPPaE4m9TukZ6zNS2YA_CrLd4UVs1-_j4mzfLvMAV2uo/s320/404+error+page+6.jpg"/>
Error Page Style 5

- Go to Setting->Search Preferences
- Copy below code in Custom Page Not Found section [as shown in fig. first]
<h2 style="font-size: 35px;margin: 0;text-align: center;">Oops..! </h2>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPSKvAC-UDAxfjh8W_m-PKJF2H7vny3kCi2jxflXysbptMWmkGnJbKqVXwBljD1bhRLnoDDXoxx1SnCSIt2ZDqmxaCStVIAnwrUXxUsAacfZMl9Pj5pGs77kaykUCOXyar8XD29QUMglY/s1600/404+error+page+7.jpg"/>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPSKvAC-UDAxfjh8W_m-PKJF2H7vny3kCi2jxflXysbptMWmkGnJbKqVXwBljD1bhRLnoDDXoxx1SnCSIt2ZDqmxaCStVIAnwrUXxUsAacfZMl9Pj5pGs77kaykUCOXyar8XD29QUMglY/s1600/404+error+page+7.jpg"/>
Error Page Style 6

- Go to Setting->Search Preferences
- Copy below code in Custom Page Not Found section [as shown in fig. first]
<h2 style="font-size: 35px;margin: 0;text-align: center;">Oops..! </h2>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiM6wzWVy6-UeD5laj4oskoc6iVsrEkZLcmQfjYJrnNFKjwuNjanKUYoAhe4eEdvCjjHdMo1OpnxGVm9jK8RWoXfXVJIX_HmoVm-K1dZnJQb8SbAmmASJ9AIfjX4y_3j23OXaQYL01-M8k/s1600/404+error+page+3.jpg"/>
<h3 style="font-size:17px;">Sorry,You are trying to reach an invalid page...!<br><a href="/">Click here</a> to go to Homepage <br> Have a nice Day...</h3><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiM6wzWVy6-UeD5laj4oskoc6iVsrEkZLcmQfjYJrnNFKjwuNjanKUYoAhe4eEdvCjjHdMo1OpnxGVm9jK8RWoXfXVJIX_HmoVm-K1dZnJQb8SbAmmASJ9AIfjX4y_3j23OXaQYL01-M8k/s1600/404+error+page+3.jpg"/>
Then Click Save..That all..
First thanks to Bloggerplugins.com for the custom error page code, visit here. Then i made some changes and add beautiful 404 images that i was inspired from HongKiat .
I thinks this article helped you..If any bugs of doubts don't hesitate to ask..do comment...
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