
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/AVvXsEi4SXpb3gxXFkI5hdKSulwCtLRaygybdjJTSAs3YtjQsxbFUl6XpIBlR7GGd4dUo2w_xcPsfP_FB_lM1d7D4XAcAA3C9o4eWVy5i3AyvbHt0fRpehcIlmZFri-j9wFy2dRJjrm4YseH8ew/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/AVvXsEi4SXpb3gxXFkI5hdKSulwCtLRaygybdjJTSAs3YtjQsxbFUl6XpIBlR7GGd4dUo2w_xcPsfP_FB_lM1d7D4XAcAA3C9o4eWVy5i3AyvbHt0fRpehcIlmZFri-j9wFy2dRJjrm4YseH8ew/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/AVvXsEigoo8gcXxBmIf9ofAYgQoZ0TWjXGvv6zM1Lcje4ILs8nmRvBoy4YT7cBuiuRXZzP_iyPp5sE4y4-A9iqy-W8Rs7WMVye8mQfEWUPOhUGtN82wyHtiQNldH2LatCF2JjwGHsYIyQPiSemI/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/AVvXsEigoo8gcXxBmIf9ofAYgQoZ0TWjXGvv6zM1Lcje4ILs8nmRvBoy4YT7cBuiuRXZzP_iyPp5sE4y4-A9iqy-W8Rs7WMVye8mQfEWUPOhUGtN82wyHtiQNldH2LatCF2JjwGHsYIyQPiSemI/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/AVvXsEiv3PL_TBCHQjEKrC0_O0Zwk_f7c42MntE6Od2C2jyPWGGNrrS6GomwLgUZfJMaUOfeQQJVKMgvYyfGorVm9OY_he0sAdE3deMS9tqmNCxIuh91k9G0THptPsOM210jfuRl7QqHr5t-oVM/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/AVvXsEiv3PL_TBCHQjEKrC0_O0Zwk_f7c42MntE6Od2C2jyPWGGNrrS6GomwLgUZfJMaUOfeQQJVKMgvYyfGorVm9OY_he0sAdE3deMS9tqmNCxIuh91k9G0THptPsOM210jfuRl7QqHr5t-oVM/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/AVvXsEhaujJaG62mVlsgKmJTzy8oL-ZH2PidRR6Ln50L3uBe4S-yoNb43_WFg60euY4PS5I4kFc3vDaBnJMTGpRkut_LFcwjKPUz40hmza1NBo8RdMp3BHcAWUGA_kdCDUiGqmCEMVWNp1a_9nw/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/AVvXsEhaujJaG62mVlsgKmJTzy8oL-ZH2PidRR6Ln50L3uBe4S-yoNb43_WFg60euY4PS5I4kFc3vDaBnJMTGpRkut_LFcwjKPUz40hmza1NBo8RdMp3BHcAWUGA_kdCDUiGqmCEMVWNp1a_9nw/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/AVvXsEhaqgbShK6aQBbNdIzDcVLcwfforUBOh9ee0JeqSIttmMuiJEAo-PBUrvuHjoOpaU8KpTDZJVbRWQq5wbktDResH9OhcPSEsrYI9Tp35fC0CeLQaa7ufeASX1Wqi9z6ounIadjaIJt-LTc/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/AVvXsEhaqgbShK6aQBbNdIzDcVLcwfforUBOh9ee0JeqSIttmMuiJEAo-PBUrvuHjoOpaU8KpTDZJVbRWQq5wbktDResH9OhcPSEsrYI9Tp35fC0CeLQaa7ufeASX1Wqi9z6ounIadjaIJt-LTc/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/AVvXsEiijlBDtycE5QYcQBpj2s0yqyLNP5XYftbOC5VTnjW-QkVC3KAPHl-MzOyMolle8rV3dVwO2MqsLQjFpaLHQ79-kwdXQ7jtdOFAH-jO-T4hov9-oBCJS1o2C-iUAFWM3bKzcbMxJjoLcXc/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/AVvXsEiijlBDtycE5QYcQBpj2s0yqyLNP5XYftbOC5VTnjW-QkVC3KAPHl-MzOyMolle8rV3dVwO2MqsLQjFpaLHQ79-kwdXQ7jtdOFAH-jO-T4hov9-oBCJS1o2C-iUAFWM3bKzcbMxJjoLcXc/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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